Question

Need help

Answer 1

Find the radius of the circle with equation \[x^2+y^2+8x+8y+28=0\]

Answer 2

@Nnesha ?

Answer 3

So what you need to do is complete the square. Do this one at a time. Take the x2 and 8x and add (1/2)(8)^2=16
so you get (x+4)^2
do the same thing with y and get (y+4)^2
Then because you added 16 twice to complete the square twice, you need to subtract 16 twice. This -32 combines with the 28 to make -4
add -4 to other side and get 4
so there you have it the radius is 2
how do i know this?
Because x^2+y^2=r^2
is the general form for a circle.
Now that it is in the form you can pick out r which is on the other side of the equation as 2^2
therefore the radius is 2

Answer 4

thanks a ton

Answer 5

that should help...and no problem.