Phương pháp giải:

\(\int\limits_a^b {f\left( u \right)du}  = \int\limits_a^b {f\left( t \right)dt}  = \int\limits_a^b {f\left( x \right)dx} \).

\(\int\limits_a^b {f\left( x \right)dx}  = \int\limits_0^b {f\left( x \right)dx}  - \int\limits_0^a {f\left( x \right)dx} \).

Lời giải chi tiết:

\(\begin{array}{l}\int\limits_0^3 {f\left( u \right)du}  = \frac{5}{3};\int\limits_0^4 {f\left( u \right)du}  = \frac{3}{5}\\ \Rightarrow \int\limits_3^4 {f\left( u \right)du}  = \int\limits_0^4 {f\left( u \right)du}  - \int\limits_0^3 {f\left( u \right)du} \\ = \frac{3}{5} - \frac{5}{3} =  - \frac{{16}}{{15}}\end{array}\)