Variable Expressions with ParenthesesDate: 9/9/96 at 18:31:41 From: Anonymous Subject: Variable Expressions with Parentheses I can complete some problems like this, but often I come up with an answer that is completly wrong and do not know why. How do you solve: 2(x-1) - 3(2 - 3x) - (x + 1) I can use the distributive property to simplify the first two parts of the problem, but them I am lost... Date: 9/9/96 at 19:17:40 From: Doctor Mike Subject: Re: Variable Expressions with Parentheses Hi, The combination of the distributive property with minus signs often causes a little bit of confusion. First let's get to the place where I think you are in the problem: (2x-2) - (6-9x) - (x+1) Notice that I have left it in the form of 3 expressions, where 2 of them need to be subtracted. The key thing to remember is to subtract BOTH things inside the 2nd and 3rd expressions. For instance, to subtract 6-9x you have to subtract 6 and also subtract -9x. The -(-9x) just becomes +9x. So, after subtracting you get: 2x - 2 - 6 + 9x - x - 1 The next step is to combine like terms, that is, get all the x parts together and get all the plain numbers together. So, 10x - 9 I hope this helps. -Doctor Mike, The Math Forum Check out our web site! http://mathforum.org/dr.math/ |
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