Đáp án + Giải thích các bước giải:
`M+N=3xyz-3x^2+5xy-1+5x^2+xyz-5xy+3-y`
`=(5x^2-3x^2)+(3xyz+xyz)+(5xy-5xy)-y-1+3`
`=2x^2+4xyz-y+2`
$$$$
`M-N=3xyz-3x^2+5xy-1-(5x^2+xyz-5xy+3-y)`
`=3xyz-3x^2+5xy-1-5x^2-xyz+5xy-3+y`
`=(-3x^2-5x^2)+(3xyz-xyz)+(5xy+5xy)+y-1-3`
`=-8x^2+2xyz+10xy+y-4`
$$$$
`N-M=5x^2+xyz-5xy+3-y-(3xyz-3x^2+5xy-1)`
`=5x^2+xyz-5xy+3-y-3xyz+3x^2-5xy+1`
`=(5x^2+3x^2)+(xyz-3xyz)-(5xy+5xy)-y+3+1`
`=8x^2-2xyz-10xy-y+4`