a,Tìm x:cx2 + 36 = 12x b, Phân tích đa thức thành nhân tử : x3 + 1 – x2 – x (x + y)3 – x3 – y3

`a)x^2+36=12x`

`⇔x^2-12x+36=0`

`⇔x^2-2.x.6+6^2=0`

`⇔(x-6)^2=0`

`⇔x-6=0`

`⇔x=6`

Vậy `x=6`

`b)x^3+1-x^2-x`

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

`=x^2(x-1)-(x-1)`

`=(x^2-1)(x-1)`

`=(x+1)(x-1)(x-1)`

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

`c)(x+y)^3-x^3-y^3`

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

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

`=3xy(x+y)`