Math Is Fun Forum

Now I understand. In order for the integral to remain unchanged, you must multiply the by the reciprocal 2/5 * 5/2 = 1. Therefore it is unchanged.
So if you were to multiply the numerator by 2, you would have to multiply the whole integral by 1/2.

How much is a 1/2 pound of your brain? I'd like to buy, if possible (you only use 10% after all!).

I'll have a go when I see it.

You're a teacher? I should have known, there's difference between saying and teaching, it is a skill.

What I meant.. I understood du replaces 10x, since they are both equal, hence, du/√u
.....but why isn't there a dx at the end. Or alternatively, since dx = du/10x, a du/10x on the end? Ahhh...
Just realised...you did it slightly different, see: http://img242.imageshack.us/my.php?image=4atb6.png   
You'd still end up with the same answer.
Those pesky du's and dx's.....They never explain what it means, they just tell you it. lol

Kind regards