Question

Sử dụng lược đồ horner để phân tích các đa thức sau thành phân tử:

a) \(f\left(x\right)=x^3-6x^2+11x-6\)

b) \(f\left(x\right)x^3-19x-30\)

c) \(f\left(x\right)=x^3+4x^2+4x+3\)

d) \(f\left(x\right)=3x^4+5x^3-x^2-5x-2\)

Answer 1

a/ \(f\left(x\right)=x^3-6x^2+11x-6\)

\(=x^3-x^2-5x^2+5x+6x-6\)

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

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

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

b/ \(f\left(x\right)=x^3-19x-30\)

\(=x^3+3x^2-3x^2-9x-10x-30\)

\(=x^2\left(x+3\right)-3x\left(x+3\right)-10\left(x+3\right)\)

\(=\left(x+3\right)\left(x^2-3x-10\right)\)

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

c/ \(f\left(x\right)=x^3+4x^2+4x+3\)

\(=x^3+3x^2+x^2+3x+x+3\)

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

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