sorry, i did something wrong!! (x+y)(x^2+xy+y^2)=19 (factorise x^3+y^3=19)
should be (x+y)(x^2-xy+y^2)=19
therefore: x^2-xy+y^2 = 19 this lead to x^2 + y^2 = 19 + xy...................(1)
because: x^2 + 2xy + y^2 =1 , this lead to x^2 + y^2 = 1 - 2xy...............(2)
equation (1) -...