Question

phân tích các đa thức sau thành nhân tử

a, x^3y^3 + x^2y^2 + 4

b, x^3 + 3x^2y - 9xy^2 + 5y^3

Answer 1

a) \(x^3y^3+x^2y^2+4\)

\(=x^3y^3-x^2y^2+2x^2y^2-2xy+2xy+4\)

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

\(=xy\left(x^2y^2-xy+2\right)+2\left(x^2y^2-xy+2\right)\)

\(=\left(xy+2\right)\left(x^2y^2-xy+2\right)\)

b) \(x^3+3x^2y-9xy^2+5y^3\)

\(=x^3+5x^2y-2x^2y-10xy^2+xy^2+5y^3\)

\(=\left(5y^3-10xy^2+5x^2y\right)+\left(xy^2-2x^2y+x^3\right)\)

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

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

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