You first try to plug 4 into the function, and you get 0 in the numerator and the denominator, which tells you to move on to the next technique. The quadratic expression in the numerator screams for you to try factoring it. Notice that the numerator of the previous function factors to (x – 4)(x – 2). The x – 4 cancels on the top and the bottom of the fraction. This step leaves you with f(x) = x – 2. You can plug 4 into this continuous function to get 2.