1/x-1/y=-0,8|*5xy, при условии 5ху не = 0 x-y=4 х не =0 у не =0 5y-5x=-4xy x=4+y 5y-5(4+y)=-4y(4+y)=-16y-4y^2 5y-20-5y+16y+4y^2=0 4y^2+16y-20=0|:4 y^2+4y-5=0 По теореме Вието y1+y2=-p=-4 y1*y2=q=-5 y1=-5 y2=1 x1=4+y1=4+(-5)=4-5 x1=-1 x2=4+y2=4+1 x2=5 (-1;-5) и (5;1)
