Giúp e với e cảm ơn nhiều ạ !

`bb{a.}`

`M=(6x+2)(9x^2 -3x+1)-(x+1)(x^2 -x+1)`

`=2(3x+1)[(3x)^2 -3x.1+1^2]-(x+1)(x^2 -x.1 +1^2)`

`=2[(3x)^3 +1^3]-(x^3 +1^3)`

`=2(27x^3 +1)-(x^3 +1)`

`=54x^3 +2-x^3 -1`

`=53x^3 +1`

`=53. (0,5)^3 +1`

`=53. 0,125+1`

`=6,625+1`

`=7,625`

`bb{b.}`

`N=x^3 +y^3 +6x^2 y^2 (x+y)+3xy(x^2 +y^2)`

`=(x+y)(x^2 -xy+y^2)+6x^2 y^2 .1+3xy(x^2 +2xy+y^2 -2xy)`

`=1.(x^2 +2xy+y^2 -2xy-xy)+6x^2 y^2 +3xy[(x+y)^2 -2xy]`

`=[(x+y)^2 -3xy]+6x^2 y^2 +3xy(1^2 -2xy)`

`=(1^2 -3xy)+6x^2 y^2 +3xy.(1-2xy)`

`=1-3xy+6x^2 y^2 +3xy-6x^2 y^2`

`=1`