Question

2.Rezolvati prin metoda substituției urmatoarele sisteme:
b) {3x+ 2y=5
5x- 3y= 2
e) { 4x-3y=6
5x-7y=1
f) { x+3y= -1
2x-y= 5
3. Rezolvati prin metoda reducerii sistemul:
{x+y= -1
5x+2y=7

Answer 1

b)
{3x+ 2y=5
5x- 3y= 2
y=(5-3x)/2
5x-3(5-3x)/2=2
10x-15+9x=4
19x=19
x=1
y=(5-3)/2=1

e)
{ 4x-3y=6     y=(4x-6)/3
5x-7y=1
5x-7(4x-6)/3=1
15x-28x+42=3
13x=39
x=3
y=(4*3-6)/3=2

f)
{ x+3y= -1 
2x-y= 5
x=-1-3y
2(-1-3y)-y=5
-2-6y-y=5
7y=-7
y=-1
x=-1-3*(1)=-1-3=-4

3.
{x+y= -1     inmultim cu -2
5x+2y=7
{-2x-2y=2
5x+2y=7
3x=9   x=3
y=-1-3=-4