The time for A to walk from A to B is12/(x+8)+2/3+1/3 =12/x.

X 2+20x-96 = 0, which is used to solve the equation.

So x=4.

If the speed of A is 4km/h, then the speed of B is12 km/h.

2.X 2+2x-k = 0, if two equations are simultaneous.

Two different intersections mean that the tower is greater than 0.

So k>- 1 and k is not equal to O.

(2) simplify x1x2-2x1-x22+2x2 = (x12+x22)/x1x2.

x 1x2=-k

x 1+x2=-2