Question

Rozwiąż układ równań metodą podstawiania
a)
x + y = 7
x - y = 3

b)
3x + 2y = 2
3x - y = -10

c)
2x + 3y = 3
4x + 3y = -9

Answer 1

A)
{x + y = 7
{x - y = 3

{x= -y+7
{x-y=3

-y+7-y=3
-2y+7=3
-2y= -4   / : (-2)
y=2
x= -2+7
x=5

{x=5
{y=2


b)
{3x + 2y = 2
{3x - y = -10

{3x+2y=2
{-y= -3x-10   / : (-1)

{3x+2y=2
{y=3x+10

3x+2*(3x+10)=2
9x+20=2
9x= -18   / : 9
x= -2
y=3*(-2)+10
y=4

{x= -2
{y=4

c)
{2x + 3y = 3
{4x + 3y = -9

{2x= -3y+3   / : 2
{4x+3y= -9

{x= -3/2y+3/2
{4x+3y= -9

4*(3/2y+3/2)+3y= -9
-3y+6= -9
-3y= -15   / : (-3)
y=5
x= -3/2*5+3/2
x= -6

{x= -6
{y=5