# Definite Integral [help]

1. Jan 23, 2008

### mckallin

Definite Integral [help] !!!

hello, can anyone help me how to complete the following definite integral? Thanks!!
∫ (x^2)*sqrt(7 x + 9) dx (From 0 to 1)

Last edited: Jan 23, 2008
2. Jan 23, 2008

### Rainbow Child

Try the substitution

$$\sqrt{7x+9}=y$$

3. Jan 23, 2008

### mckallin

sorry, I still can't figure out it, can you give me some more detail? thanks a lot .

4. Jan 23, 2008

### HallsofIvy

If $y= \sqrt{7x+ 9}$, what is dx (in terms of dy and y)? What is x in terms of y? (So you can substitute for that x2.)

5. Jan 23, 2008

### mckallin

I got it, thanks for help!! ^-^