# Math Help - evaluating a definite integral

1. ## evaluating a definite integral

if I evaluate

I get e^6 - e^2 but the answer should be (1/2)(e^6 - e^2), where does the (1/2) come from?

2. ## Re: evaluating a definite integral

Hey kingsolomonsgrave.

Try doing a transformation u = 2x where du/dx = 2 which means you have to multiply by a 1/2 and the limits go from [1,3] to [2,6]

3. ## Re: evaluating a definite integral

The reason your answer is wrong is because:

$\frac{d}{dx}\left(e^{2x} \right)\ne e^{2x}$

but:

$\frac{d}{dx}\left(\frac{1}{2}e^{2x} \right)=e^{2x}$

Using the substitution suggested by chiro is the best way to go, IMHO.

thanks!