c: \(=x\left(x-3\right)+4\left(x-3\right)=\left(x-3\right)\left(x+4\right)\)
d: \(=\left(x-2y\right)\left(x+2y\right)+3\left(x-2y\right)\)
\(=\left(x-2y\right)\left(x+2y+3\right)\)
e: \(=\left(x-3\right)\left(x^2+3x+9\right)-4x\left(x-3\right)\)
\(=\left(x-3\right)\left(x^2-x+9\right)\)