Find all solutions when two functions are the same (same result)












2












$begingroup$


Can anybody help me find solutions for $x$ when: $$y_1 = y_2$$
and equations are (for example):
$$y_1 = frac{(x^2+x)}{2} ;; ;y_2 = frac{(x^2+19x-12)}{2}$$



By solving it "brute force" I can tell some of the solutions are:




  1. $$y_1(5)=y_2(2)=15$$

  2. $$y_1(15)=y_2(9)=120$$

  3. $$? ? ?$$


Thank you!










share|cite|improve this question











$endgroup$












  • $begingroup$
    So, to be clear, when $y_1$ and $y_2$ have the same output, even if $x$ might not be the same... An interesting question. Experience might suggest a clever parameterization, if not brute force, but this is just a guess. Nonetheless, good luck.
    $endgroup$
    – Eevee Trainer
    Dec 28 '18 at 10:00












  • $begingroup$
    In short, you want to solve diophantine equations (for two variables). See this . It might help a little.
    $endgroup$
    – Jaideep Khare
    Dec 28 '18 at 10:04










  • $begingroup$
    Wouldn't Diophantine equations only suffice for integer solutions? What about real values of $x$, which I feel is more in line with what OP wants.
    $endgroup$
    – Eevee Trainer
    Dec 28 '18 at 10:05










  • $begingroup$
    There many confusing things here. With usual interpretation we have $y_1=y_2$ iff $x=frac 2 3$ but you are allowing different values of $x$ on LHS and RHS. Also it is not clear if you are looking for integer solutions. There is a continuum of solutions if you don't restrict to integer values of $x$.
    $endgroup$
    – Kavi Rama Murthy
    Dec 28 '18 at 10:06












  • $begingroup$
    Hi Kavi, Yes I am looking of course integer solution, sorry for not mentioning it.
    $endgroup$
    – Jovan
    Dec 28 '18 at 10:11
















2












$begingroup$


Can anybody help me find solutions for $x$ when: $$y_1 = y_2$$
and equations are (for example):
$$y_1 = frac{(x^2+x)}{2} ;; ;y_2 = frac{(x^2+19x-12)}{2}$$



By solving it "brute force" I can tell some of the solutions are:




  1. $$y_1(5)=y_2(2)=15$$

  2. $$y_1(15)=y_2(9)=120$$

  3. $$? ? ?$$


Thank you!










share|cite|improve this question











$endgroup$












  • $begingroup$
    So, to be clear, when $y_1$ and $y_2$ have the same output, even if $x$ might not be the same... An interesting question. Experience might suggest a clever parameterization, if not brute force, but this is just a guess. Nonetheless, good luck.
    $endgroup$
    – Eevee Trainer
    Dec 28 '18 at 10:00












  • $begingroup$
    In short, you want to solve diophantine equations (for two variables). See this . It might help a little.
    $endgroup$
    – Jaideep Khare
    Dec 28 '18 at 10:04










  • $begingroup$
    Wouldn't Diophantine equations only suffice for integer solutions? What about real values of $x$, which I feel is more in line with what OP wants.
    $endgroup$
    – Eevee Trainer
    Dec 28 '18 at 10:05










  • $begingroup$
    There many confusing things here. With usual interpretation we have $y_1=y_2$ iff $x=frac 2 3$ but you are allowing different values of $x$ on LHS and RHS. Also it is not clear if you are looking for integer solutions. There is a continuum of solutions if you don't restrict to integer values of $x$.
    $endgroup$
    – Kavi Rama Murthy
    Dec 28 '18 at 10:06












  • $begingroup$
    Hi Kavi, Yes I am looking of course integer solution, sorry for not mentioning it.
    $endgroup$
    – Jovan
    Dec 28 '18 at 10:11














2












2








2


0



$begingroup$


Can anybody help me find solutions for $x$ when: $$y_1 = y_2$$
and equations are (for example):
$$y_1 = frac{(x^2+x)}{2} ;; ;y_2 = frac{(x^2+19x-12)}{2}$$



By solving it "brute force" I can tell some of the solutions are:




  1. $$y_1(5)=y_2(2)=15$$

  2. $$y_1(15)=y_2(9)=120$$

  3. $$? ? ?$$


Thank you!










share|cite|improve this question











$endgroup$




Can anybody help me find solutions for $x$ when: $$y_1 = y_2$$
and equations are (for example):
$$y_1 = frac{(x^2+x)}{2} ;; ;y_2 = frac{(x^2+19x-12)}{2}$$



By solving it "brute force" I can tell some of the solutions are:




  1. $$y_1(5)=y_2(2)=15$$

  2. $$y_1(15)=y_2(9)=120$$

  3. $$? ? ?$$


Thank you!







functions systems-of-equations






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Dec 28 '18 at 10:01









Jaideep Khare

17.8k32669




17.8k32669










asked Dec 28 '18 at 9:57









JovanJovan

164




164












  • $begingroup$
    So, to be clear, when $y_1$ and $y_2$ have the same output, even if $x$ might not be the same... An interesting question. Experience might suggest a clever parameterization, if not brute force, but this is just a guess. Nonetheless, good luck.
    $endgroup$
    – Eevee Trainer
    Dec 28 '18 at 10:00












  • $begingroup$
    In short, you want to solve diophantine equations (for two variables). See this . It might help a little.
    $endgroup$
    – Jaideep Khare
    Dec 28 '18 at 10:04










  • $begingroup$
    Wouldn't Diophantine equations only suffice for integer solutions? What about real values of $x$, which I feel is more in line with what OP wants.
    $endgroup$
    – Eevee Trainer
    Dec 28 '18 at 10:05










  • $begingroup$
    There many confusing things here. With usual interpretation we have $y_1=y_2$ iff $x=frac 2 3$ but you are allowing different values of $x$ on LHS and RHS. Also it is not clear if you are looking for integer solutions. There is a continuum of solutions if you don't restrict to integer values of $x$.
    $endgroup$
    – Kavi Rama Murthy
    Dec 28 '18 at 10:06












  • $begingroup$
    Hi Kavi, Yes I am looking of course integer solution, sorry for not mentioning it.
    $endgroup$
    – Jovan
    Dec 28 '18 at 10:11


















  • $begingroup$
    So, to be clear, when $y_1$ and $y_2$ have the same output, even if $x$ might not be the same... An interesting question. Experience might suggest a clever parameterization, if not brute force, but this is just a guess. Nonetheless, good luck.
    $endgroup$
    – Eevee Trainer
    Dec 28 '18 at 10:00












  • $begingroup$
    In short, you want to solve diophantine equations (for two variables). See this . It might help a little.
    $endgroup$
    – Jaideep Khare
    Dec 28 '18 at 10:04










  • $begingroup$
    Wouldn't Diophantine equations only suffice for integer solutions? What about real values of $x$, which I feel is more in line with what OP wants.
    $endgroup$
    – Eevee Trainer
    Dec 28 '18 at 10:05










  • $begingroup$
    There many confusing things here. With usual interpretation we have $y_1=y_2$ iff $x=frac 2 3$ but you are allowing different values of $x$ on LHS and RHS. Also it is not clear if you are looking for integer solutions. There is a continuum of solutions if you don't restrict to integer values of $x$.
    $endgroup$
    – Kavi Rama Murthy
    Dec 28 '18 at 10:06












  • $begingroup$
    Hi Kavi, Yes I am looking of course integer solution, sorry for not mentioning it.
    $endgroup$
    – Jovan
    Dec 28 '18 at 10:11
















$begingroup$
So, to be clear, when $y_1$ and $y_2$ have the same output, even if $x$ might not be the same... An interesting question. Experience might suggest a clever parameterization, if not brute force, but this is just a guess. Nonetheless, good luck.
$endgroup$
– Eevee Trainer
Dec 28 '18 at 10:00






$begingroup$
So, to be clear, when $y_1$ and $y_2$ have the same output, even if $x$ might not be the same... An interesting question. Experience might suggest a clever parameterization, if not brute force, but this is just a guess. Nonetheless, good luck.
$endgroup$
– Eevee Trainer
Dec 28 '18 at 10:00














$begingroup$
In short, you want to solve diophantine equations (for two variables). See this . It might help a little.
$endgroup$
– Jaideep Khare
Dec 28 '18 at 10:04




$begingroup$
In short, you want to solve diophantine equations (for two variables). See this . It might help a little.
$endgroup$
– Jaideep Khare
Dec 28 '18 at 10:04












$begingroup$
Wouldn't Diophantine equations only suffice for integer solutions? What about real values of $x$, which I feel is more in line with what OP wants.
$endgroup$
– Eevee Trainer
Dec 28 '18 at 10:05




$begingroup$
Wouldn't Diophantine equations only suffice for integer solutions? What about real values of $x$, which I feel is more in line with what OP wants.
$endgroup$
– Eevee Trainer
Dec 28 '18 at 10:05












$begingroup$
There many confusing things here. With usual interpretation we have $y_1=y_2$ iff $x=frac 2 3$ but you are allowing different values of $x$ on LHS and RHS. Also it is not clear if you are looking for integer solutions. There is a continuum of solutions if you don't restrict to integer values of $x$.
$endgroup$
– Kavi Rama Murthy
Dec 28 '18 at 10:06






$begingroup$
There many confusing things here. With usual interpretation we have $y_1=y_2$ iff $x=frac 2 3$ but you are allowing different values of $x$ on LHS and RHS. Also it is not clear if you are looking for integer solutions. There is a continuum of solutions if you don't restrict to integer values of $x$.
$endgroup$
– Kavi Rama Murthy
Dec 28 '18 at 10:06














$begingroup$
Hi Kavi, Yes I am looking of course integer solution, sorry for not mentioning it.
$endgroup$
– Jovan
Dec 28 '18 at 10:11




$begingroup$
Hi Kavi, Yes I am looking of course integer solution, sorry for not mentioning it.
$endgroup$
– Jovan
Dec 28 '18 at 10:11










1 Answer
1






active

oldest

votes


















1












$begingroup$

HINT:



For integers $a,b$, we wish to solve $$frac{a^2+a}2=frac{b^2+19b-12}2impliesleft(a+frac12right)^2-frac14=left(b+frac{19}2right)^2-frac{361}4-12$$ so $$left(b+frac{19}2right)^2-left(a+frac12right)^2=102implies (a+b+10)(b-a+9)=2cdot3cdot17$$ from which only eight possible combinations exist.






share|cite|improve this answer









$endgroup$













  • $begingroup$
    tnx for the hint, but can you please drop some more details, so I can actually conclude for next similar problem? Also as what I can see this would also require checking for each of them, or I am missing something?
    $endgroup$
    – Jovan
    Dec 28 '18 at 11:42










  • $begingroup$
    @Jovan The cases are $(a+b+10,b+a+9)=(1,102),(2,51),(3,34),(6,17),(17,6),(34,3),(51,2),(102,1)$. You'll need to solve all of them.
    $endgroup$
    – TheSimpliFire
    Dec 28 '18 at 13:03










  • $begingroup$
    thank you for your comments, how come that two example pairs are (5,2), (15,9) not in the list?
    $endgroup$
    – Jovan
    Dec 28 '18 at 13:22










  • $begingroup$
    @Jovan Because $(2,5)$ corresponds to $(a,b)$ not $(a+b+10,b-a+9)$ (minus sign typo in comment above). You will need to solve these simultaneous equations - albeit not difficult.
    $endgroup$
    – TheSimpliFire
    Dec 28 '18 at 13:24












  • $begingroup$
    TNX! Based on which theorem you reconstruct equations and than you got these pairs to be solved? There is no possibility to derive some general "formulation" which excludes solving all this? I mean there is no other solution, which excludes testing various cases?
    $endgroup$
    – Jovan
    Dec 28 '18 at 13:56












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1 Answer
1






active

oldest

votes








1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes









1












$begingroup$

HINT:



For integers $a,b$, we wish to solve $$frac{a^2+a}2=frac{b^2+19b-12}2impliesleft(a+frac12right)^2-frac14=left(b+frac{19}2right)^2-frac{361}4-12$$ so $$left(b+frac{19}2right)^2-left(a+frac12right)^2=102implies (a+b+10)(b-a+9)=2cdot3cdot17$$ from which only eight possible combinations exist.






share|cite|improve this answer









$endgroup$













  • $begingroup$
    tnx for the hint, but can you please drop some more details, so I can actually conclude for next similar problem? Also as what I can see this would also require checking for each of them, or I am missing something?
    $endgroup$
    – Jovan
    Dec 28 '18 at 11:42










  • $begingroup$
    @Jovan The cases are $(a+b+10,b+a+9)=(1,102),(2,51),(3,34),(6,17),(17,6),(34,3),(51,2),(102,1)$. You'll need to solve all of them.
    $endgroup$
    – TheSimpliFire
    Dec 28 '18 at 13:03










  • $begingroup$
    thank you for your comments, how come that two example pairs are (5,2), (15,9) not in the list?
    $endgroup$
    – Jovan
    Dec 28 '18 at 13:22










  • $begingroup$
    @Jovan Because $(2,5)$ corresponds to $(a,b)$ not $(a+b+10,b-a+9)$ (minus sign typo in comment above). You will need to solve these simultaneous equations - albeit not difficult.
    $endgroup$
    – TheSimpliFire
    Dec 28 '18 at 13:24












  • $begingroup$
    TNX! Based on which theorem you reconstruct equations and than you got these pairs to be solved? There is no possibility to derive some general "formulation" which excludes solving all this? I mean there is no other solution, which excludes testing various cases?
    $endgroup$
    – Jovan
    Dec 28 '18 at 13:56
















1












$begingroup$

HINT:



For integers $a,b$, we wish to solve $$frac{a^2+a}2=frac{b^2+19b-12}2impliesleft(a+frac12right)^2-frac14=left(b+frac{19}2right)^2-frac{361}4-12$$ so $$left(b+frac{19}2right)^2-left(a+frac12right)^2=102implies (a+b+10)(b-a+9)=2cdot3cdot17$$ from which only eight possible combinations exist.






share|cite|improve this answer









$endgroup$













  • $begingroup$
    tnx for the hint, but can you please drop some more details, so I can actually conclude for next similar problem? Also as what I can see this would also require checking for each of them, or I am missing something?
    $endgroup$
    – Jovan
    Dec 28 '18 at 11:42










  • $begingroup$
    @Jovan The cases are $(a+b+10,b+a+9)=(1,102),(2,51),(3,34),(6,17),(17,6),(34,3),(51,2),(102,1)$. You'll need to solve all of them.
    $endgroup$
    – TheSimpliFire
    Dec 28 '18 at 13:03










  • $begingroup$
    thank you for your comments, how come that two example pairs are (5,2), (15,9) not in the list?
    $endgroup$
    – Jovan
    Dec 28 '18 at 13:22










  • $begingroup$
    @Jovan Because $(2,5)$ corresponds to $(a,b)$ not $(a+b+10,b-a+9)$ (minus sign typo in comment above). You will need to solve these simultaneous equations - albeit not difficult.
    $endgroup$
    – TheSimpliFire
    Dec 28 '18 at 13:24












  • $begingroup$
    TNX! Based on which theorem you reconstruct equations and than you got these pairs to be solved? There is no possibility to derive some general "formulation" which excludes solving all this? I mean there is no other solution, which excludes testing various cases?
    $endgroup$
    – Jovan
    Dec 28 '18 at 13:56














1












1








1





$begingroup$

HINT:



For integers $a,b$, we wish to solve $$frac{a^2+a}2=frac{b^2+19b-12}2impliesleft(a+frac12right)^2-frac14=left(b+frac{19}2right)^2-frac{361}4-12$$ so $$left(b+frac{19}2right)^2-left(a+frac12right)^2=102implies (a+b+10)(b-a+9)=2cdot3cdot17$$ from which only eight possible combinations exist.






share|cite|improve this answer









$endgroup$



HINT:



For integers $a,b$, we wish to solve $$frac{a^2+a}2=frac{b^2+19b-12}2impliesleft(a+frac12right)^2-frac14=left(b+frac{19}2right)^2-frac{361}4-12$$ so $$left(b+frac{19}2right)^2-left(a+frac12right)^2=102implies (a+b+10)(b-a+9)=2cdot3cdot17$$ from which only eight possible combinations exist.







share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered Dec 28 '18 at 11:06









TheSimpliFireTheSimpliFire

13.2k62464




13.2k62464












  • $begingroup$
    tnx for the hint, but can you please drop some more details, so I can actually conclude for next similar problem? Also as what I can see this would also require checking for each of them, or I am missing something?
    $endgroup$
    – Jovan
    Dec 28 '18 at 11:42










  • $begingroup$
    @Jovan The cases are $(a+b+10,b+a+9)=(1,102),(2,51),(3,34),(6,17),(17,6),(34,3),(51,2),(102,1)$. You'll need to solve all of them.
    $endgroup$
    – TheSimpliFire
    Dec 28 '18 at 13:03










  • $begingroup$
    thank you for your comments, how come that two example pairs are (5,2), (15,9) not in the list?
    $endgroup$
    – Jovan
    Dec 28 '18 at 13:22










  • $begingroup$
    @Jovan Because $(2,5)$ corresponds to $(a,b)$ not $(a+b+10,b-a+9)$ (minus sign typo in comment above). You will need to solve these simultaneous equations - albeit not difficult.
    $endgroup$
    – TheSimpliFire
    Dec 28 '18 at 13:24












  • $begingroup$
    TNX! Based on which theorem you reconstruct equations and than you got these pairs to be solved? There is no possibility to derive some general "formulation" which excludes solving all this? I mean there is no other solution, which excludes testing various cases?
    $endgroup$
    – Jovan
    Dec 28 '18 at 13:56


















  • $begingroup$
    tnx for the hint, but can you please drop some more details, so I can actually conclude for next similar problem? Also as what I can see this would also require checking for each of them, or I am missing something?
    $endgroup$
    – Jovan
    Dec 28 '18 at 11:42










  • $begingroup$
    @Jovan The cases are $(a+b+10,b+a+9)=(1,102),(2,51),(3,34),(6,17),(17,6),(34,3),(51,2),(102,1)$. You'll need to solve all of them.
    $endgroup$
    – TheSimpliFire
    Dec 28 '18 at 13:03










  • $begingroup$
    thank you for your comments, how come that two example pairs are (5,2), (15,9) not in the list?
    $endgroup$
    – Jovan
    Dec 28 '18 at 13:22










  • $begingroup$
    @Jovan Because $(2,5)$ corresponds to $(a,b)$ not $(a+b+10,b-a+9)$ (minus sign typo in comment above). You will need to solve these simultaneous equations - albeit not difficult.
    $endgroup$
    – TheSimpliFire
    Dec 28 '18 at 13:24












  • $begingroup$
    TNX! Based on which theorem you reconstruct equations and than you got these pairs to be solved? There is no possibility to derive some general "formulation" which excludes solving all this? I mean there is no other solution, which excludes testing various cases?
    $endgroup$
    – Jovan
    Dec 28 '18 at 13:56
















$begingroup$
tnx for the hint, but can you please drop some more details, so I can actually conclude for next similar problem? Also as what I can see this would also require checking for each of them, or I am missing something?
$endgroup$
– Jovan
Dec 28 '18 at 11:42




$begingroup$
tnx for the hint, but can you please drop some more details, so I can actually conclude for next similar problem? Also as what I can see this would also require checking for each of them, or I am missing something?
$endgroup$
– Jovan
Dec 28 '18 at 11:42












$begingroup$
@Jovan The cases are $(a+b+10,b+a+9)=(1,102),(2,51),(3,34),(6,17),(17,6),(34,3),(51,2),(102,1)$. You'll need to solve all of them.
$endgroup$
– TheSimpliFire
Dec 28 '18 at 13:03




$begingroup$
@Jovan The cases are $(a+b+10,b+a+9)=(1,102),(2,51),(3,34),(6,17),(17,6),(34,3),(51,2),(102,1)$. You'll need to solve all of them.
$endgroup$
– TheSimpliFire
Dec 28 '18 at 13:03












$begingroup$
thank you for your comments, how come that two example pairs are (5,2), (15,9) not in the list?
$endgroup$
– Jovan
Dec 28 '18 at 13:22




$begingroup$
thank you for your comments, how come that two example pairs are (5,2), (15,9) not in the list?
$endgroup$
– Jovan
Dec 28 '18 at 13:22












$begingroup$
@Jovan Because $(2,5)$ corresponds to $(a,b)$ not $(a+b+10,b-a+9)$ (minus sign typo in comment above). You will need to solve these simultaneous equations - albeit not difficult.
$endgroup$
– TheSimpliFire
Dec 28 '18 at 13:24






$begingroup$
@Jovan Because $(2,5)$ corresponds to $(a,b)$ not $(a+b+10,b-a+9)$ (minus sign typo in comment above). You will need to solve these simultaneous equations - albeit not difficult.
$endgroup$
– TheSimpliFire
Dec 28 '18 at 13:24














$begingroup$
TNX! Based on which theorem you reconstruct equations and than you got these pairs to be solved? There is no possibility to derive some general "formulation" which excludes solving all this? I mean there is no other solution, which excludes testing various cases?
$endgroup$
– Jovan
Dec 28 '18 at 13:56




$begingroup$
TNX! Based on which theorem you reconstruct equations and than you got these pairs to be solved? There is no possibility to derive some general "formulation" which excludes solving all this? I mean there is no other solution, which excludes testing various cases?
$endgroup$
– Jovan
Dec 28 '18 at 13:56


















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