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Graphical Transformations and Finding the Original Equation of the Curve

Hello, I have a question on graph transformations which I would appreciate some help or guidance with. I have struggled with describing graphical transformations, even though it is a relatively straightforward topic I often confuse myself with the wording of the question.

A curve of y=x^2 undergoes the following transformations in the order given;
1. A translation by -2 units in the direction of the x-axis
2. A stretch by a factor of 3 in the direction of the y-axis
3. A translation of 4 units in the direction of the y-axis

Question a. Give the equation of the resulting curve.

y=x^2 undergoes transformation 1 to become y=(x+2)^2
y=x^2+2 undergoes transformation 2 to become y=3(x+2)^2
y=3(x+2)^2 undergoes transformation 3 to become y=3(x+2)^2+4

So would the equation of the resulting curve be y=3(x+2)^2+4? I am very uncertain when it comes to performing transformations so I would greatly appreciate any insight or guidance into this problem. I have also graphed and attached an image of y=3(x+2)^2+4 on desmos.

Question b. A second curve undergoes the same three transformations in the same order and the resulting curve is y=(4x+17)/(x+2). Find the equation of the original curve

If y=(4x+17)/(x+2) to find the original equation of the curve perform the reverse of the transformations in the order 3,2,1.
So would the reversal of these transformations would be a translation of -4 units in the direction of the y-axis, following by a compression of scale factor 3 in the direction of the y-axis and finally a translation of 2 units in the direction of the x-axis (to the left).
If y=(4x+17)/(x+2) undergoes this first transformation to become y=(4x+17)/(x+2-4)
Transform -4 into a fraction, -4(x+2)/(x+2)=(-4x-8)/(x+2)
y=(4x+17)/(x+2)(-4x-8)/(x+2)
Since the denominators are equal combine the fractions;
y=(4x+17-4x-8)/(x+2)
y=9/(x+2)
The curve y=9/(x+2) undergoes the second transformation, would this be a stretch of scale factor 1/3 in the direction of the y-axis?
y=9/(x+2)*(1/3)
y=9/(3(x+2))
y=3/(x+2)
The curve y=3/(x+2) undergoes the third transformation, which I think would be a translation of 2 units in the direction of the x-axis to the left.
y=3/(x+2+2), so y=3/(x+4)

The equation of the original curve would be y=3/(x+4)

Question c. Sketch the curve with the equation y=(4x+17)/(x+2)
In order to sketch a rational function, being y=(4x+17)/(x+2), one should find the asymptotes and the intercepts to plot the graph.
Begin by finding the vertical asymptote, by setting the denominator equal to zero to find any forbidden points.
x+2=0
x=-2
Thus, I cannot have x = -2, and have a vertical asymptote there, which I can sketch on my graph.
Then to find the horizontal asymptote, if the degrees of the numerator and denominator are the same, the horizontal asymptote equals the leading coefficient (the coefficient of the largest exponent) of the numerator divided by the leading coefficient of the denominator.
The horizontal asymptote would be equal to 4/1=4, so I can draw y=4 on my graph also.
Then, find any x- or y-intercepts.
When x=0, y=(4(0)+17)/(0+2), y=17/2
When y=0, 0=(4x+17)/(x+2), 4x+17=0, 4x=-17, x=-17/4

The intercepts are at (0, 17/2) and (-17/4, 0), which I can add to my sketch.
I can then input several points, say from x=-3 to x=3 to form my graph. I have plotted this graph on desmos just to demonstrate how the graph should look. Would this be correct?

I would be very grateful for any help 👍
Reply 1
Original post by AN630078
Hello, I have a question on graph transformations which I would appreciate some help or guidance with. I have struggled with describing graphical transformations, even though it is a relatively straightforward topic I often confuse myself with the wording of the question.

A curve of y=x^2 undergoes the following transformations in the order given;
1. A translation by -2 units in the direction of the x-axis
2. A stretch by a factor of 3 in the direction of the y-axis
3. A translation of 4 units in the direction of the y-axis

Question a. Give the equation of the resulting curve.

y=x^2 undergoes transformation 1 to become y=(x+2)^2
y=x^2+2 undergoes transformation 2 to become y=3(x+2)^2
y=3(x+2)^2 undergoes transformation 3 to become y=3(x+2)^2+4

So would the equation of the resulting curve be y=3(x+2)^2+4? I am very uncertain when it comes to performing transformations so I would greatly appreciate any insight or guidance into this problem. I have also graphed and attached an image of y=3(x+2)^2+4 on desmos.

Question b. A second curve undergoes the same three transformations in the same order and the resulting curve is y=(4x+17)/(x+2). Find the equation of the original curve

If y=(4x+17)/(x+2) to find the original equation of the curve perform the reverse of the transformations in the order 3,2,1.
So would the reversal of these transformations would be a translation of -4 units in the direction of the y-axis, following by a compression of scale factor 3 in the direction of the y-axis and finally a translation of 2 units in the direction of the x-axis (to the left).
If y=(4x+17)/(x+2) undergoes this first transformation to become y=(4x+17)/(x+2-4)
Transform -4 into a fraction, -4(x+2)/(x+2)=(-4x-8)/(x+2)
y=(4x+17)/(x+2)(-4x-8)/(x+2)
Since the denominators are equal combine the fractions;
y=(4x+17-4x-8)/(x+2)
y=9/(x+2)
The curve y=9/(x+2) undergoes the second transformation, would this be a stretch of scale factor 1/3 in the direction of the y-axis?
y=9/(x+2)*(1/3)
y=9/(3(x+2))
y=3/(x+2)
The curve y=3/(x+2) undergoes the third transformation, which I think would be a translation of 2 units in the direction of the x-axis to the left.
y=3/(x+2+2), so y=3/(x+4)

The equation of the original curve would be y=3/(x+4)

Question c. Sketch the curve with the equation y=(4x+17)/(x+2)
In order to sketch a rational function, being y=(4x+17)/(x+2), one should find the asymptotes and the intercepts to plot the graph.
Begin by finding the vertical asymptote, by setting the denominator equal to zero to find any forbidden points.
x+2=0
x=-2
Thus, I cannot have x = -2, and have a vertical asymptote there, which I can sketch on my graph.
Then to find the horizontal asymptote, if the degrees of the numerator and denominator are the same, the horizontal asymptote equals the leading coefficient (the coefficient of the largest exponent) of the numerator divided by the leading coefficient of the denominator.
The horizontal asymptote would be equal to 4/1=4, so I can draw y=4 on my graph also.
Then, find any x- or y-intercepts.
When x=0, y=(4(0)+17)/(0+2), y=17/2
When y=0, 0=(4x+17)/(x+2), 4x+17=0, 4x=-17, x=-17/4

The intercepts are at (0, 17/2) and (-17/4, 0), which I can add to my sketch.
I can then input several points, say from x=-3 to x=3 to form my graph. I have plotted this graph on desmos just to demonstrate how the graph should look. Would this be correct?

I would be very grateful for any help 👍

A) is good, for the final step in b) you added 2 to x in a) for a -2 shift, what do you do to reverse it?
Reply 2
Original post by mqb2766
A) is good, for the final step in b) you added 2 to x in a) for a -2 shift, what do you do to reverse it?

Thank you for your reply.
b) Oh I should have subtracted 2 for a shift to the left;
Therefore, The curve y=3/(x+2) undergoes the third transformation, which I think would be a translation of 2 units in the direction of the x-axis to the left.

y=3/(x+2-2), so y=3/x
The original curve would be y=3/x ?

Would part c be correct?
Reply 3
B) is good now and c) has good reasoning. If you're happy then all's good.
Reply 4
Original post by mqb2766
B) is good now and c) has good reasoning. If you're happy then all's good.

Thank you very much for your help and for taking the time to evaluate my workings. As I mentioned, I feel very unsteady with graphical transformations, I am uncertain why but I am sure that further practise will reduce my apprehension. I truly appreciate having someone just to put my mind at ease to evaluate the methodology I have used in formulating a solution. Thank you again 😊

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