Hello.

I have the function f(x)=2x^4 - 5

I have solved for y, and have found the inverse of this function as:-

g(x)= the 4th root of x+5 over 2. (Hard to type).

I have verified with g(f(x)), and as a result I got x. (So it looks like it's correct.)

However I am struggling to verify with f(g(x)), which should also turn out to be x, if I'm correct.

Could you please help with the last part.........

I've simplified it down to 2 x (square root of (x+5 over 2)) - 5

Thanks! :-)

## Answers (3)

f(g(x)) = 2(root4(x+5)/2))^4 - 5

= 2 (x+5) / 2 - 5 = x + 5 - 5 = x

y = 2x^4 - 5

y + 5 = 2x^4

((y+5)/2)^(1/4) = x Note that the 2 is INSIDE the radical, it is not (y+5)^(1/4)/2

using g(x) = ((x+5)/2)^(1/4) in f(x) you get

2((x+5)/2)^(1/4))^4 - 5 = 2(x +5)/2 - 5 = x + 5 - 5 = x

I dont think this function is invertible. It is not one to one. for example f(-1) = f(1) = -3. so if you want to inverse f at -3, it doesnt know whethere to go to -1 or 1.