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a-b= -(a-b)

Given
      a-b= -(a-b)
which statement is true
 
a is greater
b is greater
a and b are equal
not enough information
 
I know that the answer is C both a and b are equal, but I do not understand why.
I tried solving for a and came up with a=0, but cannot find an anser for b.
Am I on the right track?
 

2 Answers by Expert Tutors

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Vivian L. | Microsoft Word/Excel/Outlook, essay composition, math; I LOVE TO TEACHMicrosoft Word/Excel/Outlook, essay comp...
3.0 3.0 (1 lesson ratings) (1)
0
Hi Sandy;
a-b=-(a-b)
a-b=-a+b
Let's combine like terms...
Let's subtract a from both sides...
a-a-b=-a-a+b
-b=-2a+b
Let's subtract b from both sides...
-b-b=-2a+b-b
-2b=-2a
Let's divide both sides by -2...
(-2b)/-2=(-2a)/-2
b=a
 
a and b are equal.
Jonathan W. | Patient and Knowledgeable Berkeley Grad for Math and Science TutoringPatient and Knowledgeable Berkeley Grad ...
4.9 4.9 (257 lesson ratings) (257)
0
If you let x = a-b, then x = -x, and if you solve that for x, you get x = 0.  Whenever something equals its opposite, that something is 0.  Here, that something is a-b, so a-b = 0, which means a = b.