5H:
a: Ta có: \(x^2-2xy+y^2-4\)
\(=\left(x-y\right)^2-4\)
\(=\left(x-y-2\right)\left(x-y+2\right)\)
b: Ta có: \(9-x^2-2xy-y^2\)
\(=9-\left(x+y\right)^2\)
\(=\left(3-x-y\right)\left(3+x+y\right)\)
c: Ta có: \(x^2-4x+4-4y^2\)
\(=\left(x-2\right)^2-4y^2\)
\(=\left(x-2-2y\right)\left(x-2+2y\right)\)
d: Ta có: \(x^2-4xy+4y^2-4\)
\(=\left(x-2y\right)^2-4\)
\(=\left(x-2y-2\right)\left(x-2y+2\right)\)
4H:
a: Ta có: \(3xy-3x+yz-z\)
\(=3x\left(y-1\right)+z\left(y-1\right)\)
\(=\left(y-1\right)\left(3x+z\right)\)
b: Ta có: \(xy+3x+2y+6\)
\(=x\left(y+3\right)+2\left(y+3\right)\)
\(=\left(y+3\right)\left(x+2\right)\)
c: Ta có: \(x^4-2x^3+x^2-2x\)
\(=x^3\left(x-2\right)+x\left(x-2\right)\)
\(=x\left(x-2\right)\left(x^2+1\right)\)
