Integration by substitution (∫ f(g(x))g'(x)dx = ∫ f(u)du, u=g(x))

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∫ f(g(x))g'(x)dx = ∫ f(u)du, u=g(x)

What each symbol means

SymbolWhat it stands for
uSubstituted inner function
g'(x)Must appear (up to constant factor)

When to use this

Adjust constants so du matches remaining dx factor.