\(V_Q=\displaystyle\lim_{n\to\infty}\sum_{k=1}^{n}A(x_k)\,\Delta x_k\)

\(V_Q=\displaystyle\int_{a}^{b}A(x)\,dx\;=\;\displaystyle\int_{a}^{b}\left(\int_{p}^{q}f(x,y)\,dy\right)dx\)