(3x-2y)(4x-5y)-11(x+y)(x-y)+5xy=12x^2-23xy+10y^2-11x^2+11y^2+5xy=x^2-18xy+21y^2=x^2-10xy+21y^2-8xy=(x-3y)(x-7y)-8xy=(7/2-3*7/3)(7/2-7*7/3)-8*7/2*7/3=7/2*77/6-392/6=-245/12