\(14x^2-14xy-8x+8y=14x\left(x-y\right)-8\left(x-y\right)=\left(x-y\right)\left(14x-8\right)\)
\(14x^2-14xy-8x+8y\)
\(=14x\left(x-y\right)-8\left(x-y\right)\)
\(=\left(14x-8\right)\left(x-y\right)\)
\(=2\left(7x-4\right)\left(x-y\right)\)
\(14x^2-14xy-8y+8y=2\left(x-y\right)\left(7x-4\right)\)