Đáp án:
Giải thích các bước giải:
`P+Q=40x^2+50xy-6+20x^2+x^3y^5+7`
`=60x^2+50xy+x^3y^3+1`
$\\$
`P-Q=(40x^2+50xy-6)-(20x^2+x^3y^5+7)`
`= 40x^2+50xy-6-20x^2-x^3y^5-7`
`= 20x^2+50xy-x^3y^5-13`
$\\$
`Q-R=20x^2+x^3y^5+7-(-34x^3y^5-21xy+8)`
`=20x^2+x^3y^5+7+34x^3y^5+21xy-8`
`=20x^2+35x^3y^5+21xy-1`
$\\$
`Q+R=20x^2+x^3y^5+7-34x^3y^5-21xy+8`
`=20x^2-33x^3y^5-21xy+15`
$\\$
`-Q+R=-(20x^2+x^3y^5+7)-34x^3y^5-21xy+8`
`=-20x^2-x^3y^5-7-34x^3y^5-21xy+8`
`=-20x^2-35x^3y^5-21xy+1`