# How do you find the center and radius for # x^2 + y^2 - 8x + 14y + 40 = 0#?

##### 1 Answer

Jun 30, 2016

circle centre (4, -7), radius 5

#### Explanation:

Simple answer: by using algebra and completing the square - TWICE, once for x and once for y.

We're starting with:

So we complete the squares. Will do separately so it's clearer, hopefully

For the x's

For the y's

pop these back into the original, and we get

that's a circle centre (4, -7), radius 5