Tìm: a) tích phân 4^x dx;                                   b) tích phân 1/e^x dx ;

a) \(\int {{4^x}} dx = \frac{{{4^x}}}{{\ln 4}} + C\).

b) \(\int {\frac{1}{{{e^x}}}} dx = \int {{e^{ - x}}dx = - {e^{ - x}} + C} \).

c) \(\int {\left( {{{2.3}^x} - \frac{1}{3}{{.7}^x}} \right)} dx\)\( = 2\int {{3^x}dx - \frac{1}{3}} \int {{7^x}} dx\)\( = 2.\frac{{{3^x}}}{{\ln 3}} - \frac{1}{3}.\frac{{{7^x}}}{{\ln 7}} + C\).