VitalyCIB wrote:
Hi everyone!
I've come across this case in
Kaplan and still cannot understand, how to solve it in 1.5-2 minutes. Can anybody help?
\((2^3-1)(2^3+1)(2^6+1)(2^12+1)\)=
A. (2^24 -1)
B. (2^24 +1)
C. (2^48 -1)
D. (2^96 +1)
E. \(2^6\)(2^12 -1)
Hey
VitalyCIB, This question can be solved in just 20 seconds. Since U wrote "how to solve it in 1.5-2 minutes", it gave me a presumption in my mind that the question is going to be tough and hence I took 23 seconds..
So, lets start solving this question.
Formula required : \((x-y ) (x+y) = (x^2-y^2)\)
\((2^3-1)(2^3+1)(2^6+1)(2^{12}+1)\)
\(= ((2^3-1)(2^3+1))(2^6+1)(2^{12}+1)\)
\(= (2^6-1)(2^6+1)(2^{12}+1)\)
\(= ((2^6-1))(2^6+1))(2^{12}+1)\)
\(= (2^{12}-1)(2^{12}+1)\)
\(= (2^{24}-1)\)
Answer A Appreciation in the gmatclub format is always welcome..
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79% (00:45) correct 
