CAT 2017 [slot 2] Question with solution 21

$(x -1)x(x+1) = 15600$
=> $x^3 - x= 15600 $
The nearest cube to 15600 is 15625 = $25^3$
We can verify that x = 25 satisfies the equation above.
Hence the three numbers are 24, 25, 26. Sum of their squares = 1877