\(x^2-2x-4y^2-4y\)
\(=\left(x^2-4y^2\right)-\left(2x+4y\right)\)
\(=\left(x-2y\right)\left(x+2y\right)-2\left(x+2y\right)\)
\(=\left(x+2y\right)\left(x-2y-2\right)\)
a)\(x^2-2x-4y^2-4y\)
\(x^2-2x+1-\left[\left(2y\right)^2+2.2y+1\right]\)
\(\left(x-1\right)^2-\left(2y+1\right)^2\)
\(x^2-2x-4y^2-4y\)
\(=\left(x^2-2x+1\right)-\left(4y^2+4y+1\right)-2\)
\(=\left(x-1\right)^2-\left(2y+1\right)^2-2\)