Question

Cat este integrala asta? Pls

Answer 1

$\displaystyle \int x\cdot 4^x dx= \int x\cdot \left(\dfrac{4^x}{\ln 4}\right)' dx=x\cdot \dfrac{4^x}{\ln 4}-\int \dfrac{4^x}{\ln 4} dx= x\cdot \dfrac{4^x}{\ln 4}-\dfrac{4^x}{\ln^2 4}+C$