Question 151361
x=original number

Square that number and then subtract one. so we have x^2-1
Divide by one less than your original number then we have (x^2-1)/(x-1)

Now subtract your original number so the result is (x^2-1)/(x-1)-x
=(x+1)(x-1)/(x-1) - 1 = (x+1)-x  = 1

so the result is always 1 but the original number is not 1 because we can not divide by x-1(x-1 is 0 when x=1)