Răspuns:
Explicație pas cu pas:
c)notam 1/(x-2y)=t si 1/(2x-y)=u
3t-5u=2 (3) 9t-15u=6
4t+15u=7 4t+15u=7
..................
13t =13 t=1 si 3-2=5u ⇒u=1/5
1/(x-2y)=1 x-2y=1 (-2) -2x+4y=-2
1/(2x-y)=1/5 2x-y=5 2x-y=5
..................
3y=3 y=1 x=2·1+1
x=3
y=1
d) notam x-2y=t si 1/(x+3)=u
2t+u=-11/2 4t+2u=-11
3t+2u=-8 -3t-2u=8
...................
t=-3 si u=-11+6 u=-5
x-2y=-3 5x-10y=-15
-5(x+3y)=1 -5x-15y=1
.....................
-25y=-14 x=-3+2y=-3+2·14/25=103/25=4 3/5
