## College Algebra (11th Edition)

$x+k=x,k\ne0$ We can check the possibilities of this condition by setting x equal to 0 and setting k equal to 1. $(0)=(1)=1$ The final equation yields a problem. By setting k to any number except 0 and with x held constant, x can never equal its original value before the value of k was added. Therefore, the equation is a contradiction. $0\ne1$