\(4x^2-5xy+y^2=\left(4x^2-5xy+\dfrac{25}{16}y^2\right)-\dfrac{9}{16}y^2=\left(2x-\dfrac{5}{4}y\right)^2-\dfrac{9}{16}y^2=\left(2x-\dfrac{5}{4}y-\dfrac{3}{4}y\right)\left(2x-\dfrac{5}{4}y+\dfrac{3}{4}y\right)=\left(2x-2y\right)\left(2x-\dfrac{1}{2}y\right)=\left(x-y\right)\left(4x-y\right)\)
\(4x^2-5xy+y^2\)
\(=4x^2-4xy-xy+y^2\)
\(=4x\left(x-y\right)-y\left(x-y\right)\)
\(=\left(x-y\right)\left(4x-y\right)\)