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

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

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

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

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

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

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

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

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

thank bạn

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

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

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

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: \(5x^2+10xy+5y^2\)

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

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

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

a) Ta có: \(a^2-b^2-5a+5b\)

\(=\left(a-b\right)\left(a+b\right)-5\left(a-b\right)\)

\(=\left(a-b\right)\left(a+b-5\right)\)

b) Ta có: \(a^2-b^2-3ab^2-3a^2b\)

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

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

c) Ta có: \(x^2-xy+2y-4\)

\(=\left(x^2-4\right)-\left(xy-2y\right)\)

\(=\left(x-2\right)\left(x+2\right)-y\left(x-2\right)\)

\(=\left(x-2\right)\left(x+2-y\right)\)

d) Ta có: \(4a^2-10ax+15x-9\)

\(=\left(4a^2-9\right)-\left(10ax-15x\right)\)

\(=\left(2a-3\right)\left(2a+3\right)-5x\left(2a-3\right)\)

\(=\left(2a-3\right)\left(2a+3-5x\right)\)