Đáp án + Giải thích các bước giải:
`a) A(x) + B(x)`
`A(+) = -2x^4 + x^3 + x^2 + 5x - 5`
`+`
`B(x) = -x^4 - 3x^3 + 4x^2 - 6x + 7`
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`A(x) + B(x) = -3x^4 -2x^3 + 5x^2 -1x +2`
`b) A(x) - B(x) + C(x)`
`A(x) = -2x^4 + x^3 + x^2 + 5x - 5`
`-`
`B(x) = -x^4 - 3x^3 + 4x^2 - 6x + 7`
`+`
`C(x) = x^3 + x - 2`
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`A(x) - B(x) + C(x) = -x^4 + 5x^3 -3x^2 + 12x -14`