# Reflection

• July 21st 2010, 02:57 PM
MATNTRNG
Reflection
What is the image, x^2 + y^2 + 2x - 9 = 0, after a reflection in the line y = -x + 1?

I don't even know where to start...
• July 21st 2010, 06:16 PM
skeeter
Quote:

Originally Posted by MATNTRNG
What is the image, x^2 + y^2 + 2x - 9 = 0, after a reflection in the line y = -x + 1?

I don't even know where to start...

start by getting the equation for the circle in standard form (complete the square).
• July 27th 2010, 10:44 PM
simplependulum
Replace $x,y$ with $1 - y' , 1-x'$ respectively .

Then the equation obtained , $f(x',y') = 0$ is the reflected image .

The answer is $x^2 + y^2 - 2x - 4y - 5 = 0$ .