Using quotient rule, let u = 2x+12 and v = 1-x. Then we differentiate u and v separately, so u' = 2 and v' = -1. The formula for the quotient rule is: (vu' - uv')/v^2. Plugging in our values into this equation we get: vu'= 2-2x, uv' = -2x-12 and v^2 = (1-x)^2. Then vu' - uv' = 2 - 2x - (2x-12) = 2 -2x + 2x +12 = 14. So (vu' - uv')/v^2 = 14/(1-x)^2