Question

$x^{3 \\ - y3; stiind ca x-y=3 si xy= -2$

Answer 1

x - y = 3        si        xy = - 2 
x³ - y³ = ( x - y ) · ( x² + xy + y² ) = 3 · ( x²  - 2  + y ² )  =3· ( 5 - 2 ) =3·3 =9

(x -y ) ² = 3 ² 
x² - 2xy + y² = 9 
x² + y² = 9  + 2xy = 9 + 2 · ( -2) = 9 -  4 = 5