原式=1/3∫3/(3x+2)dx=1/3∫d(3x+2)/(3x+2)=ln|3x+2|/3+C
∫1/(3x+2)dx=1/3∫3/(3x+2)dx=1/3∫d(3x+2)/(3x+2)=ln|3x+2|/3+C
