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# Someone Help!!! watch

1. I can't seem to do this question can anyone help me?

Use the substitution u² = x - 1

To find ∫1/(1+√(x - 1))dx from x=5 to x=2

I changed the limits to 2 and 1
and wrote

2u(du/dx) = 1
so dx = 2u*du

But I just end up with ∫(2u)/(1+u)du

Any ideas on what to do next? Cheers.
2. You can use long division, or:
∫ 2u/(1+u) du = 2 ∫ u/(1+u)
= 2 ∫ (1+u-1)/(1+u) du
= 2 ∫ (1+u)/(1+u) - 1/(1+u) du
= 2 ∫ 1 - 1/(1+u) du
= 2 [u - ln|1+u|]
3. (Original post by joe_the_smoe)
I can't seem to do this question can anyone help me?

Use the substitution u² = x - 1

To find ∫1/(1+√(x - 1))dx from x=5 to x=2

I changed the limits to 2 and 1
and wrote

2u(du/dx) = 1
so dx = 2u*du

But I just end up with ∫(2u)/(1+u)du

Any ideas on what to do next? Cheers.

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