A few simple math questions?

Question

I was wondering if i could get some help with these, could you write the steps and the answer as I would like to know how to actually do them. thanks

1.) Determine whether f(x)=(x-1)/2 and g(x)= 2x+1 are inverses by means of composition.

2.) Convert f(x)=2x^2+8x+7 to vertex form.

3.) Find a fourth degree polynomial that has -1,-1, and 3i as zeroes.

Answer 1

1 f(g(x)) = (g(x)-1)/2 = ((2x+1)-1)/2 = 2x/2 = x  

so

f(g(x)) =x so f(x) and g(x) are inverses

2. Don't remember how

3.  f(x) = (x-1)^2(x-3i) = (x^2-2x-1)(x-3i) = x^3 +(-2 -3i)x^2 +(-1+6i)x + 3i