I will mark 2^-17 as y so 2^17 = 1/y. Difficult to write 2 to the power of -17.
2³+2²+2+1
--------------- = x times 1/y = x/y
5(y) (LCF is y)
(8+4+2+1)/5y = x/y or x = 15/5=3
Feel the answer worked out in the book is OK , must check for careless mistakes.
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What did I do wrong? Exponent Question
Source: Beat The GMAT — Problem Solving |
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thephoenix
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the very first step is wrongtorofish wrote:This question can be found in OG12th, question 230.
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we can not write (a^x+b^y)/n=n^-1/(a^-x+b^-y).....its absoultely wrng
the correct form is
n^-1/(a^x+b^y)^-1
now it can be solve as
take least power as common
i.e------> 2^-17(2^3+2^2+2^1+1)/5=2^-17(15)/5=3*2^-17
hence ans sud be 3
Is the Ans. 3? Want to make sure I have the right solution before posting to avoid any confusion
