The main issue here to consider is whether the variables are integers.
With (1), x IS an integer
With (2) xy is an integer, but this does not mean X and Y are both integers. x can be 0.5 and y can be 2, we still have xy as an integer.
Does it make a difference?
Yes. 0.5^2 = some complex number with decimals. Is a decimal number divisible by 9? No. If we multiply that decimal number by 9, is it divisible by 9? Still no.
But if x and y are integers AND xy is an integer that is divisible by 9, then we have Yes as an answer.
Thus (2) gives us mixed answers - both yes and no - thus inconsistent. Not sufficient.
With (1), the same concept applies. x is an integer but y can be a fraction.
The moment you take a decimal and put a 4th exponent to it, it's one complex decimal. And it can't be divisible by 9. Thus yes it works in the case you may have calculated, but it doesn't work in the case of a decimal.
E - since both choices give us inconsistent results.
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