Đáp án + Giải thích các bước giải:
`A+B=5x^2-4+6x^3-7+8x+4x+7x^2-6x+3`
`=6x^3+(5x^2+7x^2)+(8x+4x-6x)+(-4-7+3)`
`=6x^3+12x^2+6x-8`
`B-A=4x+7x^2-6x+3-(5x^2-4+6x^3-7+8x)`
`=4x+7x^2-6x+3-5x^2+4-6x^3+7-8x`
`=-6x^3+(7x^2-5x^2)+(4x-6x-8x)+(3+4+7)`
`=-6x^3+2x^2-10x+14`
`2A-B=2(5x^2-4+6x^3-7+8x)-(4x+7x^2-6x+3)`
`=10x^2-8+12x^3-14+16x-4x-7x^2+6x-3`
`=12x^3+(10x^2-7x^2)+(16x-4x+6x)+(-8-14-3)`
`=12x^3+3x^2+18x-25`
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`2A+B=2(5x^2-4+6x^3-7+8x)+4x+7x^2-6x+3`
`=10x^2-8+12x^3-14+16x+4x+7x^2-6x+3`
`=12x^3+(10x^2+7x^2)+(16x+4x-6x)+(-8-14+3)`
`=12x^3+17x^2+14x-19`
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`2A+3=2(5x^2-4+6x^3-7+8x)+3`
`=10x^2-8+12x^3-14+16x+3`
`=12x^3+10x^2+16x-19`
`4A+B=4(5x^2-4+6x^3-7+8x)+4x+7x^2-6x+3`
`=20x^2-16+24x^3-28+32x+4x+7x^2-6x+3`
`=24x^3+(20x^2+7x^2)+(32x+4x-6x) + (-16 - 28 + 3)`
`=24x^3+27x^2+30x-41`
`2A-3B=2(5x^2-4+6x^3-7+8x)-3(4x+7x^2-6x+3)`
`=10x^2-8+12x^3-14+16x-12x-21x^2+18x-9`
`=12x^3+(10x^2-21x^2)+(16x-12x+18x)+(-8-14-9)`
`=12x^3-11x^2+22x-31`.
