x ,y pare consecutive x = 2n si y = 2n + 2
x < y x - y = 2n - ( 2n + 2) = 2n - 2n - 2 = - 2
b. 20 + ( xz - 2z -yz ) = 20 + z· ( x -2 - y )= 20 + z · ( 2n -2 - 2n - 2 ) =
= 20 + z · ( - 4 ) = 4 · ( 5 - z )
daca y < x ; 2n , 2n + 2
x - y = 2n +2 - 2n = 2
20 + z · ( x -y -2 ) = 20 + z· ( 2 - 2 ) = 20 + z· 0 = 20