Elena solves the equation x^2=7x by dividing both sides by x to get 7. She says the solution is 7. Lin solves the equation x^2=7 by rewriting the equation to get
x^2-7=0. When she graphs the equation x^2-7=0, the x-intercepts are (0,0) and
(7,0). She says the solutions are 0 and 7. Why should Elena not divide by x?