GMAT Data Sufficiency (DS) | Re: For positive integer x, what is the units digit of x^2?

Statement 1: Since unit digit of x+1 is 9, x can be either no. with unit digit 2 or no. with unit digit 6. So x^2 will have either 4 or 6 as a unit digit. So not sufficient.

Statement 2: unit digit of (x-1)^2 is 5. So x must no. with unit digit 6. So x^2 will have unit digit 6 only. Sufficient to answer.

So B is the answer.

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