Hey I was hoping you guys could help me out.

I have to find the inverse of

f(x)= 3 + x^2 + tan((y x pi)/2))

I know how to do inverses, but I cant figure out how to do them when its with polynomials. Anouther one I have that I can't figure out is:

f(x)= (e^x)/(1+2e^x)

and

f(x)=x^5+2x^3+3x+1

If anyone could help me with just a few of them, or give me an example of how to do one like this, Im sure i could figure the rest out.

Thanks for your time and help