You can
put this solution on YOUR website!if the difference is 4 (not 5), then the numbers are n and n+4 (not n+1) ... so y=n(n+4)
setting y=0 gives n=0 and n=-4 ... the minimum value for y is midway between these values (on the axis of symmetry) at n=-2
so the numbers are -2 and 2, and the product (which you did find) is -4