Chapter 2 - Linear and Quadratic Functions - Section 2.6 Building Quadratic Models from Verbal Descriptions and from Data - 2.6 Assess Your Understanding - Page 174: 34

$(x+6)^{2}+y^{2}=7$

We are given: $\operatorname{center}(h, k)=(-6,0)$ Radius = $\sqrt 7$ The equation of a circle with center at $(h,k)$ and a radius $r$ is $$(x-h)^{2}+(y-k)^{2}=r^{2}$$ Substitute the known/given values into the equation of the circle above to obtain: \begin{align*}[x-(-6)]^{2}+(y-0)^{2}&=(\sqrt{7})^{2}\\ (x+6)^{2}+y^{2}&=7 \end{align*}