Answer
$$\frac{{{5^x}}}{{\ln 5}} + C $$
Work Step by Step
$$\eqalign{
& \int {{5^x}} dx \cr
& {\text{Integrate using }}\int {{a^u}} du = \frac{{{a^u}}}{{\ln a}} + C;{\text{ For this exercise}}{\text{, set }}u = x{\text{ and }}a = 5 \cr
& {\text{Then}} \cr
& \int {{5^x}} dx = \frac{{{5^x}}}{{\ln 5}} + C \cr} $$