Question

Знак интеграла (3х+х) dx

Answer 1

u=x, du = dx
v=3^x, dv= ln3 * 3^x dx
(1/ln3) * int ( x*ln3 * 3^x dx) = (1/ln3)* (x*3^x - int (3^xdx) ) = x*3^x / ln3 - (1/ln3)*(1/ln3)*3^x + C = x*3^x/ln3 - 3^x/ (ln3)^2 + C   

Надеюсь правильно.