Question

Dedric is trying to graph a circle on a computer software program that has a grid. The equation he is graphing is x2+y2−20x−14y+5=0 . Where would he place the center of the circle and what is its radius?(1 point)

center= (20,14) , radius=5

center= (−20,−14) , radius=8

center= (10,7) , radius=12

center= (−10,−7) , radius=5

Answer 1

Complete the square:

x^2 − 20x = (x − 10)^2 − 100
y^2 − 14y = (y − 7)^2 − 49

So
(x − 10)^2 + (y − 7)^2 − 100 − 49 + 5 = 0
(x − 10)^2 + (y − 7)^2 = 144

Thus center = (10, 7) and radius = √144 = 12.