14. Find the value of the polynomial \(x(1+y)-y(x y-1)-x^{2} y\) given \(x+y=-p\) and \(x y=q\).
14. Solution. Expanding the brackets, we get:

\(x+x y-x y^{2}+y-x^{2} y=(x+y)+x y(-x-y+1)=\) \(=q(p+1)-p=p q+q-p\).