Here, one could simply study the form of the integrand ex^3 • x2.
Knowing the rules of logarithmic differentiation, he would recognize
that ex^3 differentiates to 3x2 • ex^3, very close to the integrand.
Then give a coefficient of 1/3 to ex^3 and add a general constant C to gain
ex^3/3 + C as the solution sought.