Graphing functions with mapping vector vs transformation vector
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Teacher 1 method to graph $y=2sqrt[3]{2(x-1)}+4$ says:
- Create the transformation vector of $<1,4>$ and plot this point as an ordered pair.
- Create a table of values for the parent graph of $y=sqrt[3]x$ using easy, reasonable x values $(-8, -1, 0, 1, 8)$.
- To this parent graph table, create 2 new columns and modify the x and y values with the stretch and compression values.
- From the plotted ordered pair of $(1,4)$ move over and up according to the new modified values.
This works and creates correct ordered pairs.
Teacher 2 method:
1. Create a mapping vector of $<1/2 x+1, 2y+4>$
- Simply apply these to the parent graph ordered pairs.
teacher 2 method seems simpler. But then I ran into a function that doesn't seem to work with teacher 1 as follows:
$y=2^left(x+1right)-3$.
When I try to create the transformation vector of $<-1,-3>$ I see that this ordered pair is NOT on the graph. So applying the parent graph values to a point NOT on the graph clearly produce erroneous results.
When I use the method of creating $<x-1, y-3$ this works properly.
Why doesn't Teacher method 1 work for this simple exponential?
linear-algebra algebra-precalculus
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add a comment |
$begingroup$
Teacher 1 method to graph $y=2sqrt[3]{2(x-1)}+4$ says:
- Create the transformation vector of $<1,4>$ and plot this point as an ordered pair.
- Create a table of values for the parent graph of $y=sqrt[3]x$ using easy, reasonable x values $(-8, -1, 0, 1, 8)$.
- To this parent graph table, create 2 new columns and modify the x and y values with the stretch and compression values.
- From the plotted ordered pair of $(1,4)$ move over and up according to the new modified values.
This works and creates correct ordered pairs.
Teacher 2 method:
1. Create a mapping vector of $<1/2 x+1, 2y+4>$
- Simply apply these to the parent graph ordered pairs.
teacher 2 method seems simpler. But then I ran into a function that doesn't seem to work with teacher 1 as follows:
$y=2^left(x+1right)-3$.
When I try to create the transformation vector of $<-1,-3>$ I see that this ordered pair is NOT on the graph. So applying the parent graph values to a point NOT on the graph clearly produce erroneous results.
When I use the method of creating $<x-1, y-3$ this works properly.
Why doesn't Teacher method 1 work for this simple exponential?
linear-algebra algebra-precalculus
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Isn't this the same as math.stackexchange.com/questions/3027869/… ?
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– Gerry Myerson
Dec 6 '18 at 1:50
1
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I deleted the duplicate.
$endgroup$
– user163862
Dec 6 '18 at 6:51
add a comment |
$begingroup$
Teacher 1 method to graph $y=2sqrt[3]{2(x-1)}+4$ says:
- Create the transformation vector of $<1,4>$ and plot this point as an ordered pair.
- Create a table of values for the parent graph of $y=sqrt[3]x$ using easy, reasonable x values $(-8, -1, 0, 1, 8)$.
- To this parent graph table, create 2 new columns and modify the x and y values with the stretch and compression values.
- From the plotted ordered pair of $(1,4)$ move over and up according to the new modified values.
This works and creates correct ordered pairs.
Teacher 2 method:
1. Create a mapping vector of $<1/2 x+1, 2y+4>$
- Simply apply these to the parent graph ordered pairs.
teacher 2 method seems simpler. But then I ran into a function that doesn't seem to work with teacher 1 as follows:
$y=2^left(x+1right)-3$.
When I try to create the transformation vector of $<-1,-3>$ I see that this ordered pair is NOT on the graph. So applying the parent graph values to a point NOT on the graph clearly produce erroneous results.
When I use the method of creating $<x-1, y-3$ this works properly.
Why doesn't Teacher method 1 work for this simple exponential?
linear-algebra algebra-precalculus
$endgroup$
Teacher 1 method to graph $y=2sqrt[3]{2(x-1)}+4$ says:
- Create the transformation vector of $<1,4>$ and plot this point as an ordered pair.
- Create a table of values for the parent graph of $y=sqrt[3]x$ using easy, reasonable x values $(-8, -1, 0, 1, 8)$.
- To this parent graph table, create 2 new columns and modify the x and y values with the stretch and compression values.
- From the plotted ordered pair of $(1,4)$ move over and up according to the new modified values.
This works and creates correct ordered pairs.
Teacher 2 method:
1. Create a mapping vector of $<1/2 x+1, 2y+4>$
- Simply apply these to the parent graph ordered pairs.
teacher 2 method seems simpler. But then I ran into a function that doesn't seem to work with teacher 1 as follows:
$y=2^left(x+1right)-3$.
When I try to create the transformation vector of $<-1,-3>$ I see that this ordered pair is NOT on the graph. So applying the parent graph values to a point NOT on the graph clearly produce erroneous results.
When I use the method of creating $<x-1, y-3$ this works properly.
Why doesn't Teacher method 1 work for this simple exponential?
linear-algebra algebra-precalculus
linear-algebra algebra-precalculus
asked Dec 6 '18 at 0:58
user163862user163862
88521017
88521017
$begingroup$
Isn't this the same as math.stackexchange.com/questions/3027869/… ?
$endgroup$
– Gerry Myerson
Dec 6 '18 at 1:50
1
$begingroup$
I deleted the duplicate.
$endgroup$
– user163862
Dec 6 '18 at 6:51
add a comment |
$begingroup$
Isn't this the same as math.stackexchange.com/questions/3027869/… ?
$endgroup$
– Gerry Myerson
Dec 6 '18 at 1:50
1
$begingroup$
I deleted the duplicate.
$endgroup$
– user163862
Dec 6 '18 at 6:51
$begingroup$
Isn't this the same as math.stackexchange.com/questions/3027869/… ?
$endgroup$
– Gerry Myerson
Dec 6 '18 at 1:50
$begingroup$
Isn't this the same as math.stackexchange.com/questions/3027869/… ?
$endgroup$
– Gerry Myerson
Dec 6 '18 at 1:50
1
1
$begingroup$
I deleted the duplicate.
$endgroup$
– user163862
Dec 6 '18 at 6:51
$begingroup$
I deleted the duplicate.
$endgroup$
– user163862
Dec 6 '18 at 6:51
add a comment |
1 Answer
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I think you know why method 1 didn't work for the exponential. It's because, exactly as you say, $(-1,-3)$ is not on the graph. Use the transformation vector $(-1,-3)$, but apply the parent graph values to the point $(-1,-2)$, which is on the graph, and see if that doesn't work.
Basically, when you strip away everything from the first equation, you're left with $y=root3of x$, which goes through the origin; but when you do the same for the second equation, you get $y=2^x$, which doesn't. That's the difference.
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$begingroup$
Thank you. I think I will use the second method which always works.
$endgroup$
– user163862
Dec 6 '18 at 17:59
add a comment |
Your Answer
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1 Answer
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$begingroup$
I think you know why method 1 didn't work for the exponential. It's because, exactly as you say, $(-1,-3)$ is not on the graph. Use the transformation vector $(-1,-3)$, but apply the parent graph values to the point $(-1,-2)$, which is on the graph, and see if that doesn't work.
Basically, when you strip away everything from the first equation, you're left with $y=root3of x$, which goes through the origin; but when you do the same for the second equation, you get $y=2^x$, which doesn't. That's the difference.
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$begingroup$
Thank you. I think I will use the second method which always works.
$endgroup$
– user163862
Dec 6 '18 at 17:59
add a comment |
$begingroup$
I think you know why method 1 didn't work for the exponential. It's because, exactly as you say, $(-1,-3)$ is not on the graph. Use the transformation vector $(-1,-3)$, but apply the parent graph values to the point $(-1,-2)$, which is on the graph, and see if that doesn't work.
Basically, when you strip away everything from the first equation, you're left with $y=root3of x$, which goes through the origin; but when you do the same for the second equation, you get $y=2^x$, which doesn't. That's the difference.
$endgroup$
$begingroup$
Thank you. I think I will use the second method which always works.
$endgroup$
– user163862
Dec 6 '18 at 17:59
add a comment |
$begingroup$
I think you know why method 1 didn't work for the exponential. It's because, exactly as you say, $(-1,-3)$ is not on the graph. Use the transformation vector $(-1,-3)$, but apply the parent graph values to the point $(-1,-2)$, which is on the graph, and see if that doesn't work.
Basically, when you strip away everything from the first equation, you're left with $y=root3of x$, which goes through the origin; but when you do the same for the second equation, you get $y=2^x$, which doesn't. That's the difference.
$endgroup$
I think you know why method 1 didn't work for the exponential. It's because, exactly as you say, $(-1,-3)$ is not on the graph. Use the transformation vector $(-1,-3)$, but apply the parent graph values to the point $(-1,-2)$, which is on the graph, and see if that doesn't work.
Basically, when you strip away everything from the first equation, you're left with $y=root3of x$, which goes through the origin; but when you do the same for the second equation, you get $y=2^x$, which doesn't. That's the difference.
answered Dec 6 '18 at 10:07
Gerry MyersonGerry Myerson
147k8149302
147k8149302
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Thank you. I think I will use the second method which always works.
$endgroup$
– user163862
Dec 6 '18 at 17:59
add a comment |
$begingroup$
Thank you. I think I will use the second method which always works.
$endgroup$
– user163862
Dec 6 '18 at 17:59
$begingroup$
Thank you. I think I will use the second method which always works.
$endgroup$
– user163862
Dec 6 '18 at 17:59
$begingroup$
Thank you. I think I will use the second method which always works.
$endgroup$
– user163862
Dec 6 '18 at 17:59
add a comment |
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$begingroup$
Isn't this the same as math.stackexchange.com/questions/3027869/… ?
$endgroup$
– Gerry Myerson
Dec 6 '18 at 1:50
1
$begingroup$
I deleted the duplicate.
$endgroup$
– user163862
Dec 6 '18 at 6:51