Integration Help - u Substiution. [ ]

[Physics197]

Integration Help - u Substiution. [urgent]

Homework Statement

Evaluate the following integrals.
(Here are the functions with respect to x)

1. x^2/(x+1)^5

2. (4x^2+4x+1)^10

3. x^2[sqr(1-x)]

4. (x+1)(x-3)^10

5. sqr(x)[sqr(4+xsqr(x))]

Looking more for how to solve them, not what the answer is..
Im good when its in the simple form, its just when its not multiplied by the derivative of the inside I get stuck.

Homework Equations

The Attempt at a Solution

 

[djeitnstine]

For the first one, u = x+1. thus du = dx right? so what is x in the numerator? Just solve for x, nothing special about it to get stuck on =] *hint you get a quadratic in 'u' on top which makes the integral simple.

 

[Random Variable]

the second one is just (2x+1)^20

 

[Physics197]

Thank you, and as for the first one, you must multiple the numerator by u^-5

 

[Mark44]

Thank you, and as for the first one, you must multiple the numerator by u^-5

That doesn't make any sense to me. If you multiply an expression by something, its value changes unless you multiply by 1. Now maybe what you did is valid, but you aren't explaining it very clearly.