If $LaTeX: \displaystyle f(x)=0$ and $LaTeX: \displaystyle g(x)=- 4 x^{2} + 9 x + 6$ find $LaTeX: \displaystyle (f\circ g)(x)$ .

Evaluating $LaTeX: \displaystyle f(x)$ at $LaTeX: \displaystyle g(x)$ gives $LaTeX: \displaystyle (f\circ g)(x)=f(g(x))=0$ .