Bunuel wrote:
What is the value of 5x^2 + 4x - 1 ?
(1) x(x + 2) = 0
(2) x = 0
\(5x^2+4x-1\)
\(=5x^2+5x-x-1\)
\(=5x(x+1)-1(x+1)\)
\(=(x+1)(5x-1)\)
Statement 1: x(x + 2) = 0
Either x=0 or x=-2
If x=0,
\(5x^2+4x-1=(+1)(-1)=-1\)
If x=-2
\(5x^2+4x-1=(-2+1)(-10-1)=(-1)(-11)=11\)
InsufficientStatement 2: x = 0
It will lead to a single value of expression as seen above.
Sufficient.Answer: BNOTE: In the case of first statement, it is absolutely necessary to check the value of the expression for any two given values of x.
Since quadratics represent a parabola on a XY plane, there will be 2 values of X for any given value of the quadratic expression(except the lowest or the highest value).
Question makers can trick test takers into this trap.
_________________
~R.
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78% (00:53) correct 
