Exponents question

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Source: — Data Sufficiency |

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by Neo Anderson » Sun Mar 04, 2012 6:03 am
If s and t are integers, what is the value of s - t?

1. s^t= 1
2. s + t = 5


with only 1, we can arrive at the following:-
a) s = any integer, t = 0
b) s=1, t= any integer
c) s=-1, t= even integer

clearly we dont get a unique answer here, hence 1 is Insufficient.

now with only 2, clearly s and t do not get a unique value as for ex s=2, t=3 and s=3, t=2
thus again Insufficient.

taking 1 and 2 together:-
a) s = any integer, t = 0 => s can be 1,2,3,4,5 and also -ve values
b) s=1, t= any integer => t= 2,3,4,5 etc and also -ve values
c) s=-1, t= even integer => t= 2,4,6 etc and also -ve values

again we dont have a unique answer here, thus E

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by Troika » Sun Mar 04, 2012 5:27 pm
Neo, thanks for the solution!