`a)` Ta có :
`f(x) + h(x) = g(x)`
`=> h(x) = g(x) - f(x)`
`=> h(x) = (x^4- x^3 + x^2 + 5) - (x^4 - 3x^2 + x-1)`
`=> h(x) = x^4 - x^3 + x^2 +5 - x^4 + 3x^2 - x +1`
`=> h(x) = (x^4 -x^4) - x^3 + (x^2 +3x^2) -x + (5+1)`
`=> h(x) = -x^3 + 4x^2 -x+6`
Vậy `h(x) = -x^3 + 4x^2 -x+6`
`b) f(x) - h(x) = g(x)`
`=> h(x) = f(x) - g(x)`
`=> h(x) = (x^4 - 3x^2 + x-1) - (x^4-x^3+x^2+5)`
`=> h(x) = x^4 - 3x^2 + x -1 - x^4 + x^3 -x^2-5`
`=> h(x) = (x^4 -x^4) +x^3 - (3x^2 +x^2) + x - (1+5)`
`=> h(x) = x^3 - 4x^2 + x -6`
Vậy `h(x) = x^3 - 4x^2 + x -6`
