\(\left(a+b\right)^3-3ab.\left(a+b\right)=\left(a+b\right)\left[\left(a+b\right)^2-3ab\right]=\left(a+b\right)\left(a^2+b^2-ab\right)\)

`(a+b)^3-3ab(a+b)`

`=(a+b)(a+b)^2-3ab(a+b)`

`=(a+b)[(a+b)^2-3ab]`

`=(a+b)(a^2+2ab+b^2-3ab)`

`=(a+b)(a^2-ab+b^2)`

\(\left(a+b\right)^3-3ab\left(a+b\right)=a^3+3a^2b+3ab^2+b^3-3a^2b-3ab^2=a^3+b^3=\left(a+b\right)\left(a^2-ab+b^2\right)\)

\(a^3-b^3+3a^2+3ab+b^2\)

\(=\left(a-b\right)\left(a^2+ab+b^2\right)+3\left(a^2+ab+b^2\right)\)

\(=\left(a-b+3\right)\left(a^2+ab+b^2\right)\)

\(2ab^2-a^2b-b^3=b^2\left(2a-a^2-b\right)\)

\(2ab^2-a^2b-b^3\)

\(=-b\left(a^2-2ab+b^2\right)\)

\(=-b\left(a-b\right)^2\)

-(2ab² - a²b - b³)

= b(-2ab + a² + b²)

= b(a² - 2ab + b²)

= b(a - b)²

\(a^3+b^3+c^3-3ab\)

\(=a^3+ab\left(a+b\right)+b^3-3ab\left(a+b\right)\)

\(=\left(a+b\right)^3-3ab\left(a+b\right)\)

\(=\left(a+b\right)\left(a^2+2ab+b^2-ab\right)-3ab\left(a+b\right)\)

\(=\left(a+b\right)\left(a^2+b^2-ab\right)\)

\(a^3+3a^2b+3ab^2+b^3-8c^3\)

\(=\left(a+b\right)^3-8c^3\)

\(=\left(a+b-2c\right)\left[\left(a+b\right)^2+2\left(a+b\right)c+4c^2\right]\)

\(=\left(a+b-2c\right)\left(a^2+b^2+2ab+2ac+2bc+4c^2\right)\)

thank bạn

giải bài toán: cho tam giác MNP, NTlà phân giác của góc N biết MN=4cm, NT=10cm, MP=8cm:TínhTM, TP? 

a: \(3ab-6a^2b\)

\(=3ab\cdot1-3ab\cdot2a\)

=3ab(1-2a)

b: \(x^3-6x\)

\(=x\cdot x^2-x\cdot6\)

\(=x\left(x^2-6\right)\)

c: \(x^2-y^2-9x+9y\)

\(=\left(x^2-y^2\right)-\left(9x-9y\right)\)

\(=\left(x-y\right)\left(x+y\right)-9\left(x-y\right)\)

\(=\left(x-y\right)\left(x+y-9\right)\)

d: \(5x^2+10xy+5y^2\)

\(=5\left(x^2+2xy+y^2\right)\)

\(=5\left(x+y\right)^2\)

=(a-b)(a²+ab+b²) + (a-b)(a-b)

=(a-b)(a²+ab+b²+a-b)

 (a^3-b^3)+(a-b)^2

=(a-b)(a²+ab+b²)+(a-b)²

=(a-b)[(a²+ab+b²)+(a-b)]

=(a-b)(a²+ab+b²+a-b)