# another dilations question

• Feb 14th 2008, 02:05 AM
chaneliman
another dilations question
has 7/x^2 been dilated from the y-axis by a factor of 1/7 or 7?
• Feb 14th 2008, 02:19 AM
mr fantastic
Quote:

Originally Posted by chaneliman
has 7/x^2 been dilated from the y-axis by a factor of 1/7 or 7?

I hope you got more from this thread than just an answer.

In other words, I hope you learnt something from it.

Since I live in hope, I will suggest that you try applying what you've learnt from it.

Alternatively, at least give your thoughts on what you think the answer might be and why.
• Feb 14th 2008, 02:22 AM
DivideBy0
Quote:

Originally Posted by chaneliman
has 7/x^2 been dilated from the y-axis by a factor of 1/7 or 7?

I assume you mean dilated from $\displaystyle y=\frac{1}{x^2}$,

Let x' and y' be the image points after dilation and x, y be the original points before dilation.

$\displaystyle y'=\frac{7}{(x')^2}$

$\displaystyle \Rightarrow \frac{y'}{7}=\frac{1}{(x')^2}$

Letting, $\displaystyle (x,y)=(x, \frac{y'}{7} )$

That means $\displaystyle y = \frac{y'}{7}$ and $\displaystyle x'=x$

$\displaystyle \Rightarrow y' = 7y$ and $\displaystyle x' = x$

Therefore, as each new image point y' is 7 times the original point y, there has been a dilation of 7 from the x-axis.