Finding length of the curve, did i mess up simpifying?

[mr_coffee]

Hello everyone, i'm suppose to find the length of the curve. But the book got a different answer, anyone see my problem? Here is the picture and my work:
http://img216.imageshack.us/img216/7900/urnt8jd.jpg
THanks.

[TD]

Doesn't (2t)² = 4t²?

[mr_coffee]

ahh ur right my bad..
so i have sqrt(4t^2 + 25t^8)
Will that simpify too:
10t^5?