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Mentallic
Mentallic is offline
#5
Feb22-11, 01:51 AM
HW Helper
P: 3,436
You've forgotten to expand (k+1)2 correctly again. If you did, you would get -30k instead of -32k.

By the way, the question asked for you to solve it by completing the square. You've used the quadratic formula, which you could've used right at the start anyway before dividing through by 2k.