a) \(3xy^2-6x^2y+3x^3=3x\left(y^2-2xy+x^2\right)=3x\left(y-x\right)^2\)
b) \(x^2-xy+4y-4x=x\left(x-y\right)+4\left(y-x\right)=\left(x-4\right)\left(x-y\right)\)
c) \(9y^2-1-4x^2+4x=\left(3y\right)^2-\left(4x^2-4x+1\right)=\left(3y\right)^2-\left(2x-1\right)^2=\left(3y-2x+1\right)\left(3y+2x-1\right)\)


