a) `f(x) = -3x^2 + x -1 + x^4 - x^3 - x^2 + 3x^4`
`f(x) = (-3x^2 - x^2) + (x^4 + 3x^4) + x-1 - x^3`
`f(x) = -4x^2 + 4x^4 + x-1 - x^3`
b) `g(x) = x^4 + x^2 - x^3 + x-5 + 5x^3 - x^2`
`g(x) = x^4 + (x^2 - x^2) -(x^3 - 5x^3) + x -5`
`g(x) = x^4 - (-4x^3) + x-5`
`f(x) = x^4 + 4x^3 + x-5`