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integration question (hl)

waheyyy · 2010-01-03 16:12:35

hey im just wondering, when you're intergrating and you use the substitution method , i.e u=... and then du/dx, do u have to change the limits in all circumstances or is it ok to slot back in the value for u after integrating? i've been doing the latter and getting the correct answer, but looking at the marking scheme now…

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03-01-2010 5:12pm

#1

waheyyy

Closed Accounts Posts: 89 ✭✭

Join Date: April 2007

Posts: 72

hey im just wondering, when you're intergrating and you use the substitution method , i.e u=... and then du/dx, do u have to change the limits in all circumstances or is it ok to slot back in the value for u after integrating? i've been doing the latter and getting the correct answer, but looking at the marking scheme now it says that 'not calculating substituted limits' is a blunder

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#2 03-01-2010 5:18pm
PunkFreud

Registered Users Posts: 308 ✭✭

Join Date: August 2009

Posts: 288

yes, it is ok what you are doing.

It is only a blunder if you leave in "u", not if you substitute in back the original value for "u".

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