The answer is 125. If you were to pair 250 people in 2, that would be 250 divided by 2. And 250 divided by 2 is 125.
9999 is largest 4 digit number, and 100^2 is 10000, or 1 greater than the largest 4 digit number. This means that the closest square root of the largest perfect square is most likely 99. So 99^2 (9801)is the largest perfect square of four digits.
Substitute -3 to x
(-3)^2 + 4(-3) + 1
9 - 12 + 1
= -2