Need help with Integration Question (1 Viewer)

[Flurix]

I have been struggling with this question for a while and it is similar to questions in my exam next week!
I keep getting 64 units squared as my answer and the textbook says the answer is 21 1/3.

Please help me!
Thanks in advance!

 

[jazz519]

https://drive.google.com/open?id=1Iy_BhGhKCoRPZ2iBerYKmHYL6YJv6VYN

 

[Flurix]

Thanks!. Made me realise I wasn't writing the question out right the whole time!

 

[jazz519]

Thanks!. Made me realise I wasn't writing the question out right the whole time!

No worries