Algebra....

Quote:

Originally Posted by Ant

I Really have no idea about how to approach this one...

2/[y(y+1)] can be expressed in form 2/y - 2/y+1

thanks

That's called "partial fractions". Suppose $\frac{2}{y(y+1)}= \frac{A}{y}+ \frac{B}{y+1}$ . Multiply on both sides by y(y+1) to get rid of the fractions: $2= A(y+1)+ By$ . That must be true for all y so you can take any value for y you want. In particular, taking y= 0 give 2= A and taking y= -1 gives 2= -B.