Why is B insufficient?
Is x = ky?
From condition 1 we know y(3y+7) = x ==> x = ky where 3y+7 = k, k will always be an interger as y is an integer hence we proved x =ky sufficient
From condition 2 we know (x^2 - x) = ky ==>ky = x(x-1) ==> x = (k/x-1) * y ==> here k/x-1 will not be an integer and hence not sufficient
Answer is A for me.
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