`a,(3/7.x^4.y^2).(14/15.x^3.y^4) `
`=3/7.x^4.y^2 . 14/15.x^3.y^4 `
`=(3/7. 14/15).(x^4.x^3).(y^2.y^4) `
`=2/5.x^7.y^6 `
hệ số `2/5`
biến `x^7y^6`
`b,(5/7.x.y^3).(-7/10.x^4.y^2).(2/3.x^3.y^4) `
`=5/7.x.y^3.(-7/10).x^4.y^2 . 2/3.x^3.y^4 `
`=[5/7.(-7/10) . 2/3].(x.x^4.x^3).(y^3.y^2.y^4 )`
`=-1/3.x^8.y^9`
hệ số `-1/3`
biến `x^8y^9`