Question

Va rog ,doar cele 2 exercitii ! Va multumesc!!

Answer 1

4.

a)

x+2y=4 | *2

-2x+y=-3

2x+4y=8

-2x+y=-3

5y=5

y=5/5

y=1

-2x+1=-3

x=2

b)

-2x+y=1 |*(-2)

3x+2y=-5

4x-2y=-2

3x+2y=-5

7x=-7

x=-7/7

x=-1

-2*(-1)+y=1

2+y=1

y=1-2

y=-1

c)

-x+2y=1 |*(-3)

-3x+6y=2

3x-6y=-3

-3x+6y=2

0=-1

deci (x,y) apartine multimii vide.

d)

2x+y=1

-2x-y=-1 din ce avem aici totul este egal cu 0

0=0

x apartine multimii R

5.

a)

x/2-y/3=2 |*6

x/6+y=4 |*6

3x-2y=12

x+6y=24 |*(-3)

3x-2y=12

-3x-18y=-72

-20y=-60

y=-60/-20

y=3

3x-2*3=12

x=6

b)

x/3+y/4=7 |*12

-x/4+y/3=1 |*12

4x+3y=84 |*3

-3x+4y=12 |*4

12x+9y=252

-12x+16y=48

25y=300

y=300/25

y=12

-3x+4*12=12

-3x+48=12

-3x=12-48

-3x=-36

x=-36/-3

x=12

c)

x/2+y/5=1 |*10

x/3-y/5=2 |*15

5x+2y=10

5x-3y=30 |*(-1)

5x+2y=10

-5x+3y=-30

5y=-20

y=-20/5

y=-4

5x+2*(-4)=10

5x-8=10

5x=10+8

5x=18

x=18/5