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Stuck on a core 4 integration question

20150614_175524-1.jpg
It's to integrate x(x^2-4)^(1/2)
It seems to work when i use the substitution u=x^2-4 but don't all substitutions have to be linear??
I feel like I'm just being stupid because it's only question 1..
Original post by amylucinda
20150614_175524-1.jpg
It's to integrate x(x^2-4)^(1/2)
It seems to work when i use the substitution u=x^2-4 but don't all substitutions have to be linear??
I feel like I'm just being stupid because it's only question 1..


Why do you think that all substitutions have to be linear?
Think about adding one to the power of bracket , without the x and differentiate
Reply 3
Avatar for amylucinda
amylucinda
OP
1
Original post by lizard54142
Why do you think that all substitutions have to be linear?


Oh do they not have to be linear?:K:
Wow my teacher must have taught us another thing wrong..:frown:
Thanks!
Original post by amylucinda
Oh do they not have to be linear?:K:
Wow my teacher must have taught us another thing wrong..:frown:
Thanks!


They most certainly do not! I am very surprised if your teacher told you that.

:smile:
Reply 5
Avatar for Gome44
Gome44
10
Original post by amylucinda
20150614_175524-1.jpg
It's to integrate x(x^2-4)^(1/2)
It seems to work when i use the substitution u=x^2-4 but don't all substitutions have to be linear??
I feel like I'm just being stupid because it's only question 1..


A quicker way to do it is by inspection, but a substitution works just as well :smile:
Reply 6
Avatar for amylucinda
amylucinda
OP
1
Original post by Gome44
A quicker way to do it is by inspection, but a substitution works just as well :smile:

Thank you very much! I Get it now:smile:

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