On function representation (11 17:39:58) Let f (x) = CX / 2x + 3 (x ≠ - 3 / 2) satisfy f (f (x)) = x & # 160; find the value of real number C

On function representation (11 17:39:58) Let f (x) = CX / 2x + 3 (x ≠ - 3 / 2) satisfy f (f (x)) = x & # 160; find the value of real number C

f(f(x))
=c[cx/(2x+3)]/{2[cx/(2x+3)]+3}
Multiply by 2x + 3
=c^2x/[2cx+3(2x+3)]
=c^2x/[(2c+6)x+9]
=x
So C ^ 2 = (2C + 6) x + 9
(2c+6)x=c^2-9
This formula holds when x ≠ - 3 / 2
So 2C + 6 = C ^ 2-9 = 0
So C = - 3

Set (18:17:50:24)
Let a = {X / (x-4) (x-a) = 0}, B = {X / (x-1) (x-4) = 0] if a is contained in B, find the value of A

A ={x/（x-4）（x-a）=0},
x=4,x=a
B={X/（x-1）（x-4）=0]
x=1,x=4
A is contained in B
So: a = 1