What is the integral of (21x)dx from 1/2 to 3?

1 Answer
Sep 23, 2016

5ln(6)

Explanation:

Integrate each of these by part. Note that ddx(2x)=2, so 2dx=2x, and ddx(ln(x))=1x, so 1xdx=ln(x):

312(21x)dx=[2xln(x)]312

=[2(3)ln(3)][2(12)ln(12)]

=6ln(3)1+ln(12)

Note that ln(3)+ln(12)=ln(3)ln(2)=(ln(3)+ln(2))=ln(6):

=5ln(6)