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colakumarfanta
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Target question: Is (x-1)(x+1) divisible by 2?colakumarfanta wrote:Q. Is (x-1)*(x + 1) divisible by 2 ?
a) x is not divisible by 3
b)(x-1) is divisible by 2
or
Target question: Is (x-1)(x+1) even?
Statement 1: x is not divisible by 3
Several possible cases here.
case a: x=1 --> (x-1)(x+1) = (1-1)(1+1) = 0, which is divisible by 2
case b: x=2 --> (x-1)(x+1) = (2-1)(2+1) = 3, which is not divisible by 2
Since we cannot definitively answer the target question, statement 1 is INSUFFICIENT
Statement 2: (x-1) is divisible by 2
If (x-1) is divisible by 2, then x-1 is even
If x-1 is even, then x is odd
If x is odd, then x+1 is even
So, (x-1)(x+1) = (even)(even) = even
Since we can definitively answer the target question, statement 2 is SUFFICIENT
The answer is B
Cheers,
Brent
