\(=\left(x-y\right)\left(x+y\right)-5\left(x-y\right)=\left(x-y\right)\left(x+y-5\right)\)
\(=\left(x-y\right)\left(x+y\right)-5\left(x-y\right)=\left(x+y-5\right)\left(x-y\right)\)
\(x^2-y^2-5x+5y=\left(x+y\right)\left(x-y\right)-5\left(x-y\right)=\left(x-y\right)\left(x+y-5\right)\)
x2-y2-5x+5y=(x2-y2)-(5x-5y)=(x-y)(x+y)-5(x-y)=(x-y)[(x+y)-5]=(x-y)(x+y-5)
\(x^2-y^2-5x+5y=\left(x^2-y^2\right)-\left(5x-5y\right)\\ =\left(x-y\right)\left(x+y\right)-5\left(x-y\right)\\ =\left(x-y\right)\left(x+y-5\right)\)