\begin{align*}
  (\int_0^nf(x)dx) \\
  (\frac{3}{4}) \\ \\
  \left(\int_0^n
    f\left(x\right)dx\right) \\
  \left(\frac{3}{4}\right) \\
  \left[\left(\frac{1}{3}\right)
    x^3+C\right]_0^n
\end{align*}