a) \(=4x\left(x-3y\right)\)
b) \(=5\left(x-y\right)-x\left(x-y\right)=\left(x-y\right)\left(5-x\right)\)
c) \(=\left(x^2+10x+25\right)-y^2=\left(x+5\right)^2-y^2=\left(x-y+5\right)\left(x+y+5\right)\)
d) \(=2\left(x^2-2x-3\right)=2\left[x\left(x+1\right)-3\left(x+1\right)\right]=2\left(x-3\right)\left(x+1\right)\)


