Question

Rozwiąż układy równań metodą podstawiania.

1] 2x-2y=7
4x+3y=21

2] 0,4x +0,3y=1,4
0,1x+3y=2,3

Answer 1

2x-2y=7
4x+3y=21

2x=7+2y/*2
4x=14+4y
14+4y+3y=21
7y=21-14
7y=7
y=1
2x-2=7
2x=7+2
2x=9
x=9/2=4,5

Answer 2

1] 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
14+7y=21
x=3,5+y
7y=21-14
x=3,5+y
7y=7/:7
x=3,5+y
y=1
x=3,5+1
y=1
x=4,5
y=1

2] 0,4x +0,3y=1,4/*10
0,1x+3y=2,3/*10
4x+3y=14
x+30y=23
4x+3y=14
x=23-30y
4*(23-30y)+3y=14
x=23-30y
92-120y+3y=14
x=23-30y
92-117y=14
x=23-30y
-117y=14-92
x=23-30y
-117y=-78/:-117
x=23-30y
y=0,6
x=23-30*0,6
y=0,6
x=5
y=0,6