# Math Help - integration by substitution

1. ## integration by substitution

Using an appropriate substitution, find .

Can anyone help me with this problem? Cheers x

2. Originally Posted by Haris
Using an appropriate substitution, find .

Can anyone help me with this problem? Cheers x
Make the substitution $z=5t-5\implies t=\tfrac{1}{5}(z+5)$. Thus, $\,dt=\tfrac{1}{5}\,dz$.

The integral now becomes $\tfrac{1}{25}\int-(z+5)z^5\,dz=-\tfrac{1}{25}\int(z^6+5z^5)\,dz$

Can you take it from here?

--Chris

3. I got $-1/25[(1/7)z^7+(5/6)z^6+C]$ but it must be wrong because i entered the answer into my online assessment and it says its wrong?

4. Originally Posted by Haris
I got $-1/25[(1/7)z^7+(5/6)z^6+C]$ but it must be wrong because i entered the answer into my online assessment and it says its wrong?
You have to replace back what z is ......!