I am very confused on this although it should be very basic. The derivative of (4-x)^-1 is (4-x)^-2, since you use the chain rule. Then why is the derivative of (4-x)^-2 not 2(4-x)^-3, but -2(4-x)^-3? Shouldn't it be positive since you multiply the -3 to the front and then multiply by the derivative of the inside function (4-x) so you multiply by -1 making it positive? I'm so confused?