The graph of g(x)g(x) is the graph of f(x)=x+6f(x)=x+6 reflected across the x-axis. Which equation describes g?

g(x)=−6x−6g(x)=−6x−6

g(x)=−x+6g(x)=−x+6

g(x)=x−6g(x)=x−6

g(x)=−x−6