I have to integrate K(1-t)^4 dt between 0 and y
I get: K(1/5)(1-t)^5 the book has k(1-t)^5/(-5) i dont know how they got -5
then when i evaluate at 0 and y i get:
(k/5)[(1-y)^5 -1] and at this spot the book has (k/5)[1-(1-y)^5]
You're integrating , right? Be sure to account for the coefficient of t, which is negative one. That's the only difference between your answer and the correct one. And whenever in doubt, just try differentiating the answer you determined along with the answer given by the textbook. You'll probably notice the difference.