Question

What is the radius of a circle whose equation is x2 + y2 + 8x – 6y + 21 = 0? units

Answer 1

2

Explanation:

x²+8x+y²-6y= -21;

(x+4)²+(y-3)²-25= -21;

(x+4)²+(y-3)²=2²;

it means r²=2²; ⇒ r=2.