My textbook states.

$\displaystyle -2\sum_{i=k-4}^{2}i=-(7-k)(k-2)$

But I got the summation to equal -2k+4. I don't see how the textbook got the LHS to equal to the RHS. Thanks in advance.

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- Nov 23rd 2009, 02:38 AMSimplicitySummation
My textbook states.

$\displaystyle -2\sum_{i=k-4}^{2}i=-(7-k)(k-2)$

But I got the summation to equal -2k+4. I don't see how the textbook got the LHS to equal to the RHS. Thanks in advance. - Nov 23rd 2009, 03:41 AMalexmahone