Question

Rozwiaz uklad rownan metoda podstawiania,wyznaczajac najpierw niewiadoma x z pierwszego rownania.

a)x+4=1
2x-3y=-3

b)x+2/3y=3
y=7-2x

c)6-x=5
2x+3y=-7

Answer 1

a) x=1-4                       c) -x=5-6 /: (-1)

2(1-4)-3y=-3                  2x+3y=-7

 

x=1-4                          x=-5+6

2-8-3y=-3                     2(-5+6)+3y=-7

 

x=1-4                          x=-5+6

-3y=-3+8-2                   -10+12+3y=-7

 

x=1-4                         x=-5+6

-3y=3/-3                      3y=-7+10-12

 

x=1-4                          x=-5+6

y=-1                           3y=-9/:3

 

x=-3                             x=-5+6

y= -1                           y=-3

 

x=1

y=-3

Answer 2

a)

x+4y=1
2x-3y=-3

 

x=1-4y

2(1-4y)-3y=-3

2-8y-3y=-3

-11y=-5

y=⁵/₁₁

 

x=1-4*⁵/₁₁

x=1-1⁹/₁₁

x=-⁹/₁₁

 

 

b)

x+2/3y=3
y=7-2x

 

x=3-2/3y

x=3-2/3(7-2x)

x=3-4²/₃+1⅓x

x-1⅓x=3-4⅔

-⅓x=-1⅔

x=5

 

y=7-2*5

y=7-10

y=-3

 

c)

6y-x=5/:(-1)
2x+3y=-7

 

x=-5+6y

2(-5+6y)+3y=-7

-10+12y+3y=-7

15y=3

y=0,2

 

x=-5+6*0,2

x=-5+1,2

x=-3,8