Question

Rezolvati prin metoda substitutiei sisstemele:
a) {x=2
{3x+2y=9
b) {x=-y+1
{2x-y=3
c) {y=-5x+1
{4x+y=0

Answer 1

{x=2
{3x+2y=9=>6+2y=9=>2y=3=>y=3/2=1,5
b) {x=-y+1
{2x-y=3=>2(-y+1)-y=3=>-2y+2-y=3=>-3y=1=>y=-1/3
x=-y+1=1/3+1=4/3
 c) {y=-5x+1
{4x+y=0=>4x-5x+1=0=>-x=-1=>x=1
y=-5+1=-4

Answer 2

a)  3·2+2y=9 ⇔ 6+2y=9⇔ 2y=3 ⇔y=3/2
b) 2(-y+1)-y=3 ⇔ -2y+2-y=3 ⇔ -3y=-1 ⇔ y=1/3 ;⇔x=-1/3+ 1= 2/3
c) 4x+(-5x+1)=0 ⇔4x-5x+1=0 ⇔ -1x=-1 ⇔ x=1; y=-5+1 ⇔y=-4