Answer
$(x+4)^2+y^2=100$
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 $(-4, 0)$ and a radius of 10 units.
Thus, the standard form of the circle's equation is:
$(x-(-4))^2+(y-0)^2=10^2
\\(x+4)^2+y^2=100$
