By using partial fraction method,
∫I dx=∫1(x−3)(x+4)dx
1(x−3)(x+4)=Ax−3+Bx+41=A(x+4)+B(x−3)
On comparing the coefficients of constant and x term, we get
0=A+B & 4A−3B=1⇒A=17 & B=−17
⇒∫I dx=17∫1x−3dx−17∫1x+4dx
=17loge(x−3)−17log3(x+4)
=17loge(x−3x+4)+C