Question

Phân tích đa thức sau thành nhân tử

x²-9-4(x+3)

Answer 1

\(x^2-9-4\left(x+3\right)\)

\(=\left(x-3\right)\left(x+3\right)-4\left(x+3\right)\)

\(=\left(x+3\right)\left(x-3-4\right)\)

\(=\left(x+3\right)\left(x-7\right)\)

Answer 2

\(x^2-9-4\left(x+3\right)\)

\(=\left(x^2-9\right)-4\left(x+3\right)\)

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

\(=\left(x-3\right)\left(x+3\right)-4\left(x+3\right)\)

\(=\left(x+3\right)\left(x-3-4\right)\)

\(=\left(x+3\right)\left(x-7\right)\)