1 a)A\(=x^2-2xy+y^2+3x-3y-4\)
\(=\left(x^2-2xy+y^2\right)+\left(3x-3y\right)-4\)
\(=\left(x-y\right)^2-1+3\left(x-y\right)-3\)
\(=\left(x-y+1\right)\left(x-y-1\right)+3\left(x-y-1\right)\)
\(=\left(x-y-1\right)\left(x-y+1+3\right)\)
\(=\left(x-y-1\right)\left(x-y+4\right)\)