Math basics › More calculus
Integration by substitution
The chain rule backwards
Look for a function and its derivative both present. Let u be the inside function, and du takes care of the rest.
Change everything
If you substitute, the dx has to become du and any limits have to become u-limits. Half-converted integrals are where the marks go.
Come back
For an indefinite integral, put x back at the end. The answer should not have a u in it.