How do you integrate (2x32+1)x using substitution?

1 Answer
Mar 29, 2018

(2x32+1)xdx=14(2x32+1)2+C

Explanation:

Our goal with substitution is to find an expression whose differential appears in the integral, and represent it using the variable u.

We have (2x32+1)xdx

In this case, u=2x32+1 is the best possible choice. Were we to choose u=x,du=12xdx, and this differential is not even close to anything in the integral.

Calculate its differential:

du=(2)(32)x12dx

du=2xdx

Divide both sides by 2:

12du=xdx

And we see xdx does in fact show up in the integral. So, rewrite with the substitution:

12udu=12(12)u2+C=14u2+C

Rewriting in terms of x yields

(2x32+1)xdx=14(2x32+1)2+C