Question

Rezolvati prin metoda substitutiei sistemele:
a)2(x+y)-3y=-11
-4x+3(x+y)=18
b)3(x+2)-2=2
3x+4(7-y)=10
c)2(x+1)+3y=7
3x+2(y-5)=-10
VA ROG MULT

Answer 1

a)2x+2y-3y=-11=>2x-y=-11=>-y=-11-2x=>y=11+2x
-4x+3x+3y=18=>-x+3y=18
Inlocuim,pe,y,in,a,doua,si,avem
-x+3(11+2x)=18
-x+33+6x=18
5x=-15=>x=-3;y=5

b)3x+6=4=>3x=-2=>x=-2/3
3x+28-4y=10=>3x-4y=-18
Inlocuim,pe,x
(-2/3)3-4y=-18=>-4y=-16=>y=4

c)2x+2+3y=7=>2x+3y=5=>2x=5-3y=>x=(5-3y)/2
3x+2y-10=-10=>3x=-2y
Inlocuim,pe,x
3(5-3y)/2=-2y=>(15-9y)/2=-2y=>15-9y=-4y=>15=5y=>y=3
x=-4/2=>x=-2