a) `P(x) +Q(x)= x^3 +3x^2 +3x-2 -x^3 -x^2 -5x +2`
`= (x^3 - x^3) + (3x^2 - x^2) + (3x - 5x) - (2-2)`
`= 2x^2 - 2x`
b)`P(x) -Q(x) = ( x^3 + 3x^2 + 3x-2) - (x^3 - x^2 -5x+2)`
`P(x) -Q(x)= x^3 + 3x^2 + 3x-2 + x^3 +x^2 + 5x -2`
`= (x^3 + x^3) + (3x^2 + x^2) + (3x + 5x) - (2+2)`
`= 2x^3 + 4x^2 + 8x -4`
c) Ta có: `H(x) =P(x) + Q(x)`
`=> H(x)= 2x^2 - 2x`
Xét `H(x) =0`
`=> 2x^2 -2x =0`
`=> 2x(x -1) =0`
`=>` \(\left[ \begin{array}{l}2x=0\\x-1=0\end{array} \right.\)
`=>` \(\left[ \begin{array}{l}x=0\\x=1\end{array} \right.\)
Vậy nghiệm của `H(x)` là `0` và `1`
