Cho hàm số f ( x ) = { 0 , 5 x                     k h i     0 ≤ x < 2 1                                     k h i     2 ≤ x <

{\displaystyle \underset{0}{\overset{15}{\int }}f\left(x\right)\text{d}x}={\displaystyle \underset{0}{\overset{2}{\int }}f\left(x\right)\text{d}x}+{\displaystyle \underset{2}{\overset{15}{\int }}f\left(x\right)\text{d}x}={\displaystyle \underset{0}{\overset{2}{\int }}\text{0}\text{,}\text{5}x\text{d}x}+{\displaystyle \underset{2}{\overset{15}{\int }}\text{1}\text{d}x}0,5 điểm

={\frac{1}{4}{x}^2|}_0^2+{x|}_2^{15}=1+13=14.0,5 điểm