Chapter 8.8, Problem 107E

To determine

To prove: The identity ${\displaystyle {\int }_{-\infty }^{a}f\left(x\right)dx}+{\displaystyle {\int }_a^{\infty }f\left(x\right)dx}={\displaystyle {\int }_{-\infty }^{b}f\left(x\right)dx}+{\displaystyle {\int }_b^{\infty }f\left(x\right)dx}$.