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$$\int (f(x))' dx = f(x) + c$$

if $u=g(x)$ then

$$\int (f(u))'du = f(u)+c$$

But

$$\int (f(g(x)))'dx = f(g(x))+c$$

Where did I go wrong?

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    You replaced $u = g(x), du = dx.$ If $u = g(x)$ then $du = g'(x) dx.$2012-08-03

1 Answers 1