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 Author: questioner [ Tue Feb 22, 2011 4:44 pm ] Post subject: GMAT Algebra If (1/4)ª × 2³ = (1/2)³ª then a =A. -3B. -2C. 0D. 3E. 4(A) (1/4)ª × 2³ = 2 to the (3 – 2a)-th power.(1/2)³ª = 2 to the (-3a)-th power.Equality holds if powers are equal.3 – 2a = -3aa = -3The correct answer is choice (A).-----------I don't understand how we are able to get the powers to have like numbers below them here. I understand that if your are able to get the variables or number the same then you can just set the powers equal but don't know how to come up with ther here. Thank you.

Author:  Gennadiy [ Tue Feb 22, 2011 5:02 pm ]
Post subject:  Re: GMAT Algebra

(1/4)ª × 2³ = (1/2)³ª

We're looking for the same base, 2.
Using properties of exponents, we can see that current bases are powers of 2:

Then we can plug in the simplified terms and use properties of exponents to arrive to the final equation form:

If these transformations are NOT clear to you, you should go over the properties of exponents:
http://www.800score.com/gmat-guide.html