#### Answer

$(x+2)^2+y^2=36$

#### Work Step by Step

RECALL:
The standard equation of a circle whose center is at $(h, k)$ and has a radius of $r$ units is:
$(x-h)^2 + (y-k)^2 = r^2$
The given circle has its center at $(-2, 0)$ and a radius of 6 units.
Thus, the standard form of the circle's equation is:
$(x-(-2))^2+(y-0)^2=6^2
\\(x+2)^2+y^2=36$