How do you factor n^2-4n=0

     n² - 4n = 0
n(n) - n(4) = 0
    n(n - 4) = 0
n = 0    or    n - 4 = 0
                     + 4 + 4
                        n = 4

Solution Set: {0, 4}

First one is 1 second one is 3