Question

If r is a integer then (r2-1)r(3r+2)is divisible by

Answer 1

st -1 mentions that 2R is exactly divisible by 3

meaning R has to be multiple of 3.

sufficient.

st-2 - 3R is exactly divisible by 3. meaning R could be 2 in which case 3R=6 is exactly divisible by 3.

and R could be 3 in which case 3R = 9 is exactly divisible by 3.

But in case 1, then R is not divisible by 3, and in 2nd case R is divisible by 3.

so not sufficient.