Question

 Найдите значение выражения  (x(x^2+3y^2)-y(y^2+3x^2)/(1/x-1/y) при x=7s qrt2?y=2 s qrt2

Answer 1

((x^3-y^3)-3xy(x-y))xy/(y-x)=(x-y)(x^2+y^2-2xy)*xy/(y-x)=-xy(x-y)^2=

=-7*2*2(5sqrt(2))^2=-7*4*25*2=-1400