Question

Rezolvati multimile prin metoda substitutiei....
a)5y-4=0, 5x-3y-11=0
b)3x-7=0, 6x-5y+11=0
Rezolvati multimile prin metoda reducerii...
a)x+y=7, x+y=7
b)2x-y=11, 2x+y=9
Va roggg ajutatima

Answer 1

a)5y-4=0, 5x-3y-11=0
5y=4
y=4/5
5x-3·4/5=11
5x-12/5=11
5x=11+12/5
5x=(11·5+12)/5
5x=67/5
x=67/(5x5)
x=67/25

b)3x-7=0, 6x-5y+11=0
3x=7
x=7/3
6·7/3-5y=-11
42/3-5y=-11
14-5y=-11
-5y=-11-14
-5y=-24                     ·(-1)
y=24/5

a){x+y=7           
    {x+y=7 nu se poate prin metoda reducerii numai a substitutiei
x=7-y
7-y+y=7
nu are solutii

b){2x-y=11
   { 2x+y=9
     4x   / =20
x=20/4
x=5
din 2x+y=9⇒y=9-2x
y=9-2·5
y=-1