Bunuel wrote:
Tough and Tricky questions: properties of numbers.
Is the positive integer x odd?
(1) x = y^2 + 4y + 6, where y is a positive integer.
(2) x = 9z^2 + 7z - 10, where z is a positive integer.
St 1: x = y^2 + 4y + 6, where y is positive integer
Can be written as x=y^2+4y+4+2 or x=(y+2)^2+2
Now if y=even than x=even
but if y=odd then x=odd..
we have 2 cases so Option A and D ruled out
St 2: x = 9z^2 + 7z - 10
If z=even then we have Even (9z^2)+Even(7z)- Even(10)=Even
if z=Odd, then we have Odd+Odd-Even =Even..
Clearly x is even whether z is odd or even..
Ans is B
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