Question

Rezolva prin metoda reducerii si a sbustitutiei urmatoarele ex:

a){x-y=3 b){y=x-3
{y=x-1 {3x+y=-3

Answer 1

a)

substitutie

x-y=3

y=x-1

x-x+1=3

y=x-1

1=3 (fals)

=> sistemul nu are solutii

reducere

x-y=3

y=x-1

x-y=3

y-x=-1

x-y+y-x=2

0=2 (fals)

=> sistemul nu are solutii

b)

substitutie

y=x-3

3x+y=-3

3x+x-3=-3

4x-3=-3

4x=0

x=0

y=0-3

y=-3

reducere

y=x-3

3x+y=-3

y-x=-3 | ×3

3x+y=-3

3y-3x=-9

y+3x=-3

4y=-12

y=-3

-3-x=-3

-x=0

x=0