Question

Phân tích:
a, \(a^3+b^3+c^3-3abc\)\(a^3+b^3+c^3-3abc\)
b, \(2x^2-5x+3\)

Answer 1

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

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

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

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

\(=\left(a+b+c\right)\left(a^2+b^2+c^2+2ab+2bc+2ca-3ac-3bc-3ab\right)\)

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

\(2x^2-5x+3=2x\left(x-1\right)-3\left(x-1\right)=\left(x-1\right)\left(2x-3\right)\)