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by shanice » Thu Jun 21, 2012 8:02 pm
Simplify : x-1/2 - 2x-1/3


My workings are as follows:-

3x-3/6 - 4x-2/6 = 3x-3-4x+2/6= -x-1/6

So, my answer is -x-1/6. However, the book states -x+1/6 as the answer.

Can someone help please?

Thank you.
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Source: — Problem Solving |

by Anurag@Gurome » Thu Jun 21, 2012 9:27 pm
shanice wrote:Simplify : x-1/2 - 2x-1/3
If there is no brackets or parentheses, then this will simplify as follows...
  • # x - 1/2 - 2x - 1/3
    = -x - 1/2 - 1/3
    = -x - 3/6 - 2/6
    = -x - 5/6
But if the expression is (x - 1/2) - (2x - 1/3), then the simplification will be,
  • # (x - 1/2) - (2x - 1/3)
    = (x - 1/2 - 2x + 1/3)
    = -x - 3/6 + 2/6
    = -x - 1/6
shanice wrote:3x-3/6 - 4x-2/6 = 3x-3-4x+2/6= -x-1/6
You can't do that.
(x - 1/2) and (2x - 3/6) are different.
(x - 1/2) can be written as (x - 2/4) or (x - 3/6) or (x - 50/100) but you cannot simply change the coefficient of x. Coincidentally in this case the difference you got is same, but this is wrong.
Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
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by shanice » Sat Jun 23, 2012 9:34 am
Understood, Sir.

Thank you.
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