First, factor out the constant 4 from the denominator:
∫−104x2+8x+8dx=∫−104(x2+2x+2)dx Then,
∫−104(x2+2x+2)dx=41∫−10x2+2x+2dx Complete the square for the expression in the denominator:
x2+2x+2=(x2+2x+1)+1=(x+1)2+1 Substitute this back into the integral:
41∫−10(x+1)2+1dx Use the substitution u=x+1, so du=dx. When x=−1, u=−1+1=0. When x=0, u=0+1=1. 41∫01u2+1du The integral of u2+11 is arctan(u). Thus, we have: 41[arctan(u)]01=41(arctan(1)−arctan(0)) Since arctan(1)=4π and arctan(0)=0, we have: 41(4π−0)=16π