\[\frac{x^{2} - y^{2}}{4x + y} + 4x - y =\]
\[= \frac{x^{2} - y^{2}}{4x + y} + (4x - y)^{\backslash 4x + y} =\]
\[= \frac{x^{2} - y^{2} + (4x - y)(4x + y)}{4x + y} =\]
\[= \frac{x^{2} - y^{2} + 16x^{2} - y^{2}}{4x + y} =\]
\[= \frac{17x² - 2y²}{4x + y}\]