Question

how can i solve it x^2 +y^2-4x+18y+85=36

Answer 1

My best advice would be to put it in a graphing calculator, in the form of:

\[x ^{2}+y ^{2}-4x+18y+49=0\]

and look for where the circle comes to a point. (For example, at x=-4 and y=-9).
There's 4 answers if you're looking for x and y coordinates.

Answer 2

"Comes to a point" is a horrible way of putting it. Basically, look for the top center, right center, left center, and bottom center of the circle.