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Isolating a variable

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Isolating a variable

by calande » Fri May 30, 2008 7:15 am
If b ≠ 1, what is the value of a in terms of b if (ab) / (a-b) = 1 ?

(A) b / (1-b)
(B) (b - 1) / b
(C) b / (b + 1)
(D) (b + 1) / b
(E) (1 - b) / b

8)
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by egybs » Fri May 30, 2008 8:46 am
(ab)/(a-b) = 1

ab= a-b

ab -a = -b

a(b-1)= -b

a= (-b)/(b-1) = b/(1-b)

Answer is A.
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by calande » Fri May 30, 2008 1:24 pm
That's it! :)
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by egybs » Fri May 30, 2008 1:43 pm
There was also a big hint in the question: They said b can't = 1. The only answer where this would cause a problem is A.

Note that they didn't say b can't = - 1 ( which would cause problems for c).

-dg
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by calande » Fri May 30, 2008 10:53 pm
That's right!
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