\(F=x^2\left(2x-3\right)+y^2\left(2y-3\right)\)
\(F=2x^3-3x^2+2y^3-3y^2\)
\(F=2\left(x^3+y^3\right)-3\left(x^2+y^2\right)\)
\(F=2\left[\left(x+y\right)^3-3xy\left(x+y\right)\right]-3\left[\left(x+y\right)^2-2xy\right]\)
\(F=2\left(1-3xy\right)-3\left(1-2xy\right)\)
\(F=2-6xy-3+6xy\)
\(F=-1\)