c) \(3x^2-6x+9y^2=3\left(x^2-2x+3y^2\right)\)
h) \(3y^2-3z^2+3x^2+6xy=3\left(x^2-z^2+x^2+2xy\right)\)
\(=3\left[\left(x+y\right)^2-z^2\right]=3\left(x+y+z\right)\left(x+y-z\right)\)
g) \(3x^2+5y-3xy-5x=\left(3x^2-3xy\right)+\left(5y-5x\right)=3x\left(x-y\right)+5\left(y-x\right)=\left(x-y\right)\left(3x-5\right)\)