U-substitution in definite integrals is just like substitution in indefinite integrals except that, since the variable is changed, the limits of integration must be changed as well. If you don’t change the limits of integration, then you’ll need to back-substitute for the original variable at the end.

Read MoreEvaluating a definite integral means finding the area enclosed by the graph of the function and the x-axis, over the given interval [a,b].

Read MoreWe know that Riemann sums estimate area, and we know that integrals find exact area.

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