Integration by substitution

In calculus, integration by substitution, also known as u-substitution, reverse chain rule or change of variables, is a method for evaluating integrals and antiderivatives. It is the counterpart to the chain rule for differentiation, and can loosely be thought of as using the chain rule "backwards."

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Calculus
${\displaystyle f(a)-f(b)=\int _{b}^{a}f'(t)\,dt}$
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