trouble with last part

[Ryan Rigdon]

i have my problem set up just having a little trouble with the last part of it. i tried doing the example thats just like it but cant get their answer for the example here it is. its set up right just the integrating thats bothering me. Any hints?

 

[wjm11]

just the integrating thats bothering me. Any hints?

I didn't check all your other work, but for the final step:

You can move the constants (.35pi/7.5^2) “out front” of the integral (to the left). Then just “multiply out” (expand) the three binomials:

((y + 9)^2)(9 - y)
= (y^2 + 18y + 81)(9 – y)
= 9y^2 + 162y + 729 – y^3 – 18y^2 – 81y
= -y^3 – 9y^2 + 81y +729

Now the integration is easy.

 

[Ryan Rigdon]

thanx i will give that a shot.

 

[Ryan Rigdon]

i got the problem right just thought you would like to see my findings. thanx for the hint.