Question

Mấy bn cho mik hỏi câu này  vs

Phân tích thành nhân tử

a.x^3 -7x - 6

b.x^3 - 19x - 30

c.a^3 - 6a^2 + 11a _6 

Answer 1

a) \(x^3-7x-6\)

\(=\left(x^3+2x^2\right)-\left(2x^2+4x\right)-\left(3x+6\right)\)

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

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

b)\(x^3-19x-30\)

\(=\left(x^3-5x^2\right)+\left(5x^2-25x\right)+\left(6x-30\right)\)

\(=\left(x-5\right)\left(x^2+5x+6\right)\)

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

c) \(a^3-6a^2+11a-6\)

\(=\left(a^3-a^2\right)-\left(5a^2-5a\right)+\left(6a-6\right)\)

\(=\left(a-1\right)\left(a^2-5a+6\right)\)

\(=\left(a-1\right)\left(a-2\right)\left(a-3\right)\)