Is A>O?
(1)A³-A< 0
(2)1-A²> 0
This problem is from the Manhattan Guides. Just a real quick clarification that I need. I've figured the answer is C. But I did it in a much simpler way as compared to the complicated explanation given in the book.
From (1)
A(A²-1)<0
Meaning either A>0 and (A²-1)<0
Or A<0 and (A²-1)>0
This gives us conflicting values of A and hence INSUFFICIENT. Is my reasoning sufficient? Do I need to do any further testing?
From (2)
A²<1
|A|<1
-1<A<1
Again giving us conflicting values hence INSUFFICIENT.
Combining both
(2) Can be written as -A²+1> 0
Multiplying by -1 we get (A²-1)<0
Using this piece of information in statement 1, Since (A²-1)<0 then A has to be positive making A>0
Hence C. I would appreciate a clarification on the bold highlighted portion. Thanks
Inequalities
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Hi,From (1)
A(A²-1)<0
Meaning either A>0 and (A²-1)<0
Or A<0 and (A²-1)>0
This gives us conflicting values of A and hence INSUFFICIENT. Is my reasoning sufficient? Do I need to do any further testing?
I don't clearly understand what you mean by conflicting values. Anyway, my take on this:
a>0 and a^2-1 <0 => 0<a<1
a<0 and a^2-1>0 => a<-1
So, from (1) we get a<-1 or 0<a<1.
So, a can be either positive or negative. If this is what you meant by conflicting values, then it is perfect.
Cheers!
Things are not what they appear to be... nor are they otherwise
Things are not what they appear to be... nor are they otherwise