Question

rozwiąż układy równań metodą podstawiania

a)2x-2y=7

4x+3y=21

b)0,4x+0,3y=1,4

01x +3y=2,3

c)2x+3y=14

3x-2y=8

d)0,5x-2y=8

2x+5y =6

Answer 1

a)2x-2y=7/:2

4x+3y=21

x-y=3,5

4x+3y=21

x=3,5+y

4(3,5+y)+3y=21

x=3,5+y

14+4y+3y=21

x=3,5+y

7y=7/:7

x=3,5+y

y=1

x=3,5+1

y=1

x=4,5

b)0,4x+0,3y=1,4/*10

0,1x +3y=2,3

4x+3y=14/:4

0,1x+3y=2,3

x+0,75y=3,5

0,1x+3y=2,3

x=2,3-0,75y

0,1(2,3-0,75y)+3y=2,3

x=2,3-0,75y

0,23-0,075y+3y=2,3

x=2,3-0,75y

2,925y=2,07/:2,925

x=2,3-0,75y

y≈0,7

x=2.3-0,75*0,7

y≈0,7

x=2,3-0,525

y≈0,7

x=1,775

c)2x+3y=14/:2

3x-2y=8

x+1,5y=7

3x-2y=8

x=7-1,5y

3(7-1,5y)-2y=8

x=7-1,5y

21-4,5y-2y=8

x=7-1,5y

-6,5y=-13/:(-6,5)

x=7-1,5y

y=2

x=7-1,5*2

y=2

x=4

d)0,5x-2y=8

2x+5y =6/:2

0,5x-2y=8

x+2,5y=3

0,5x-2y=8

x=3-2,5y

0,5(3-2,5y)-2y=8

x=3-2,5y

1,5-1,25y-2y=8

x=3-2,5y

-3,25y=6,5/:(-3,25)

x=3-2,5y

y=-2

x=3-2,5*(-2)

y=-2

x=8

 

 

licze na naj ;d