# How do you classify #13x² + 13y² - 26x + 52y = -78#?

##### 1 Answer

It has the form of a circumference, but it would have negative radius, so it represents no point in the plane.

#### Explanation:

First of all, note that we have, coefficients apart, two quadratic terms (

Also, we see that the coefficients of the quadratic terms are equal (they're both

Now we can complete the squares:

Which we can rewrite into

We know that a circumference with center

Our equation mimics this one, except for the fact that we have