What did I do wrong? Exponent Question

[torofish]

This question can be found in OG12th, question 230.

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[kstv]

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.

[thephoenix]

This question can be found in OG12th, question 230.

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the very first step is wrong

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

[gmatassistance]

Is the Ans. 3? Want to make sure I have the right solution before posting to avoid any confusion

[torofish]

yes the answer is 3
and thanks everyone