About a question format: algebra

[robinphilip01]

Hi Tommy,
The question:

If r>0,s≠1/2, and r=3s+1/1-2s, then s= ?
( algebra text book page no.172 - Question no. 5)

I understood the right answer is (C),
r-1/3+2r
My question is what is the significance of s≠1/2 ?
Is it given as an unnecessary additional data to add complication ?
It seems that information does not affect the steps for solution.
Am I right ?

[n00bpron00bpron00b]

S not equal to 1/2

Such additional information is given so as to let you know that the problem adheres to rules of math and there are no discrepancies.

If s = 1/2 the,
The denominator (1-2s) becomes "0" and anything divided by 0 is not a legal move. The problem becomes invalid

[tommywallach]

As usual, a great answer from Noob. As silly as it may sometimes seem, the GRE will always add this stipulation, so that no one could claim that equation is, at some times, undefined. I will say so that it's great on your part that you're paying attention to these givens, because as you know, they'll never throw things in there that have no effect on anything, so it is important you understand why they're giving you the things they're giving you.

-t