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# Summation of series by the method of differences watch

1. Hi everyone!

Can someone please explain how to do this "method of differences".

Heres a question
(i know how to do the first part, but i just thought id put it there because its probably needed for part b)

1(a) Given that F(r) = (r-1)r^2 , show that,

f(r+1) - f(r) = r(3r+1)

(b) Use the method of differences to find the value of,

r=50 (sigma) 99 r(3r+1)

thanks for the help!
2. Write the terms out making the substitution. Some terms should cancel out. What terms are left?

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Updated: July 22, 2009
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