din a 2-a ecuatie notam cu cit e egal x:
2x-3y=3
2x=3+3y
x=(3+3y)/2
inlocuim aceasta in ecuatia initiala:
x²-xy-y=5
((3+3y)/2)²-((3+3y)/2)y -y=5
(9+18y+9y²)/4-(3y+3y²)/2-y=5
aducem la numitorul comun:
9+18y+9y²-6y-6y²-4y=20
3y²+8y-11=0
Δ=64+132=196
√Δ=14
y1= (-8+14)/6=1
y2=(-8-14 )/6= -22/6= -11/3
x1=(3+3)/2=6/2=3
x2=(3-11)/2= -8/2= -4
