Nếu $\int_{1}^{3} f(x) d x=4$ thì $\int_{1}^{3}[f(x)+1] d x$ bằng

A. 4 . B. 2 . C. 6 . D. 5 . Ta có: $\int_{1}^{3}[f(x)+1] \mathrm{d} x=\int_{1}^{3} f(x) \mathrm{d} x+\int_{1}^{3} \mathrm{~d} x=4+2=6$.

Question

Accepted Answer

A.

4 .

B.

2 .

C.

6 .

D.

5 .

Ta có: $\int_{1}^{3}[f(x)+1] \mathrm{d} x=\int_{1}^{3} f(x) \mathrm{d} x+\int_{1}^{3} \mathrm{~d} x=4+2=6$.