Question

Phân tích các đa thức sau thành nhân tử:

\(e,x^2-y^2+6x+9\)

\(f,x^3+3x^2-9x-27\)

Answer 1

\(x^2-y^2+6x+9=\left(x+3\right)^2-y^2=\left(x+3+y\right)\left(x+3-y\right)\)

Answer 2

\(x^3+3x^2-9x-27=\left(x-3\right)\left(x^2+3x+9\right)+3x\left(x-3\right)=\left(x-3\right)\left(x^2+6x+9\right)=\left(x-3\right)\left(x+3\right)^2\)