In each of the following Exercises 6 to 9

MATHEMATICS · Subjective · A Level · Mathematics · Coordinate geometry in the (x y) plane · Coordinate geometry in the (x y) plane

Problem

In each of the following Exercises 6 to 9, find the centre and radius of the circles. 7.

x^{2}+y^{2}-4 x-8 y-45=0