Multiplying Negative IntegersDate: 11/07/2001 at 19:53:09 From: Angelica Subject: Multiplying Integers My question is on the topic Multiplying Integers. I can't figure out (-3)2 = a. Please help me! Date: 11/08/2001 at 12:25:44 From: Doctor Ian Subject: Re: Multiplying Integers Hi Angelica, Until you get more comfortable with negative numbers, you might try breaking each negative number into a positive number multiplied by -1: (-3)2 = (-1*3)2 = (-1)(3*2) = (-1)(6) = -6 Let's look at a more complicated example: (-3)(2)(-4)(-2)(3) = (-1*3)(2)(-1*4)(-1*2)(3) = (-1)(3)(2)(-1)(4)(-1)(2)(3) = (-1)(-1)(-1)(3)(2)(4)(2)(3) = (-1)(-1)(-1)(144) Now, what about all those -1's? Well, since (-1)(-1)=1, you can cancel them out in pairs: = (-1)(-1)(-1)(144) \_____/ 1 = (-1)(144) = -144 Eventually, you'll get so used to cancelling out signs that you'll start doing it directly: x x ______ ______ | | | | (-3)(2)(-4)(-2)(3)(-5)(-7) = (3)(2)(4)(2)(3)(5)(-7) = -(3 * 2 * 4 * 2 * 3 * 5 * 7) Does this help? Write back if you'd like to talk about this some more, or if you have any other questions. - Doctor Ian, The Math Forum http://mathforum.org/dr.math/ |
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