2) x + y = -6 -> x = -6 - y
xy = 8
(-6 - y)*y = 8
-y² - 6y - 8 = 0
y² + 6y + 8 = 0
delta = 36 - 32 = 4
y1 = -6 +2 / 2 = -2 , x1 = -4
y2 = -6 - 2 / 2 = -4 , x1 = -2
3) 2^-x = 2²
-x = 2 -> x = -2
4) mulțimea A are 9 cazuri posibile{11,12,13,21,22,23,31,32,33}.
3 cazuri favorabile {11,22,33}.
P (probabilitate ) = număr cazuri favorabile / număr cazuri posibile
P=1/3
5) AC + BD = 2AD
AD + DC + BA + AD = 2 AD
dar DC si BA sunt vectori opusi
-> 2AD = 2AD
6) sin(180 - x) = sin180cosx - sinxcos180
sin 180 = 0
cos 180 = -1
= sin x = 4/5
