Question

exercitile 12 si 14 va rog, dau coroana

Answer 1

12.
4x-2y+1/(x+3y)=-5 1/2 
6x-3y+2/(x+3y)=-8

4x-2y+1/(x+3y)=-11/2         inmultim cu 2
6x-3y+2/(x+3y)=-8

8x-4y+2/(x+3y)=-22/2         inmultim cu 2
6x-3y+2/(x+3y)=-8
scadem  din prima  relatie  a 2-a relatie
2x-y=-3
y=2x+3
inlocuim in prima
4x-4x-6+1/(x+6x+9)=-11/2
1/(x+6x+9)=-11/2+6
1/(7x+9=)=1/2
7x+9=2
7x=-7
x=-1
y=2×(-1)+3=-2+3=1

14.
2/(x+y-3)+3/(x-y+1)=-7/3
5/(x+y-3)+6/(x-y+1)=-13/3

notam 1/(x+y-3)=a       si 1/(x-y+1)=b

2a+3b=-7/3         inmultim cu -2
5a+6b=-13/3

-4a-6b=14/3
5a+6b=-13/3
le adunam
a=14/3-13/3=1/3
b=[-7/3-2×1/3)]/3=(-7/3-2/3)/3=-1
1/(x+y-3)=1/3   
1/(x-y+1)=-1

x+y-3=3      
x-y+1=-1  
                       
 x=6-y
6-y-y+1=-1 

7+1=2y   
8=2y   
y=4

x=6-4=2