Iam confused. I thought -10^2 is = 1003[2(25)]+1003(50)+100150+100250May you PLEASE explain what Iam doing wrong? 

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I think I see what your doing.10^2 is 100and(-10)^2 is 100,however,-10^2 is -100, because the "-" isn't included in the square operation.  So when you square the 10 in your equation, don't switch the minus sign, and you'll get the result expected.