Let . Prove that .
My 2 cents on this question:
We can write 3f(x) = 4f(x) - f(x) and move the -f(x) to the right hand side.
Let's simplify 4f(x) first, and ultimately the entire left hand side.
so
Now we need to combine this with f(4x^3 -3x):
Let
We need:
Remember that
So we have:
The left hand side argument, assuming 1-1, should equal the argument of the right hand side, x.