In general, the definition of the function composition is given by the expression below
[tex](g\circ f)(x)=g(f(x))[/tex]
Therefore, in our case,
[tex](g\circ f)(x)=g(-\frac{1}{\sqrt{x}})=1(-\frac{1}{\sqrt{x}})^3+19(-\frac{1}{\sqrt{x}})^2+16=-\frac{1}{x^{\frac{3}{2}}}+\frac{19}{x}+16[/tex]
Then, the answer is
[tex]\Rightarrow(g\circ f)(x)=-\frac{1}{x^{\frac{3}{2}}}+\frac{19}{x}+16[/tex]
