G(x) is a decreasing function at-∞, 1, and increasing function at 1, 2; (The increase or decrease of quadratic function is related to the symmetry axis. The symmetry axis of this question is x= 1, so it is divided into two parts at x= 1. )
K(x) is -5, and 0 is increasing function; (This problem is obtained through some transformation of the inverse proportional function, but it is similar to the judgment method of y=k/x, because there is a negative sign before x under the denominator, and k=2, so we know that this function is still increasing function. )
F(x) is the increasing function on (0, +∞). (The judgment method is the same as the inverse proportional function)