Question

Persamaan linear 2 variabel . Tolong di jawab ya teman
1. X + y=8 dan y=3x
2. X + 2y=12 dan 2x + y=12
3. 2x - 5y = 1 dan 4x - 3y= 9
4. 3x -5y= 24 dan 7x + 3y = 12
5. 11X + 3Y + 7 = 0 DAN 2X + 5y =0
6. 5x + y = 5 dan x - 4y =7
7. 4x - 5y = 22 dan 7x + 3y =15
8. X/4 + y/2 = 7 dan x/2 - y/2 = -4

Answer 1

1) x + y = 8
x + 3x = 8
4x = 8
x = 2
y = 3x = 3 × 2 = 6

2) x + 2y = 12|x2|2x + 4y = 24
2x + y = 12|×1|2x + y = 12
-----------------------------------(-)
3y = - 12
y = -4
x + 2y = 12
x + 2(-4) = 12
x - 8 = 12
x = 20

3) 2x - 5y = 1|×2|4x - 10y = 2
4x - 3y = 9|×1|4x - 3y = 9
-----------------------------------(-)
-7y = -7
y = 1
2x - 5y = 1
2x - 5 × 1 = 1
2x = 1 + 5
2x = 6
x = 3

4) 3x - 5y = 24|x3|9x - 15y = 72
7x + 3y = 12|×5|35x + 15y = 60
-----------------------------------(+)
44x = 132
x = 3
3x - 5y = 24
3.3 - 5y = 24
-5y = 24 - 9
y = 15 : (-5)
y = (-3)

5) 11x + 3y = -7|×5|55x + 15y = -35
2x + 5y = 0|×3|6x + 15y = 0
----------------------------------(-)
49x = - 35
x = - 35/49
x = -5/7
2x + 5y = 0
2.5/7 + 5y = 0
10/7 + 5y = 0
y = - 10/7 : 5
y = -10/7 × 1/5
y = -2/7

6) 5x + y = 5|×1|5x + y = 5
x - 4y = 7|×5|5x - 20y = 35
--------------------------------(-)
21y = 40
y = 40/21
x - 4y = 7
x - 4.40/21 = 7
x - 160/21 = 7
x = 7 + 160/21
x = 147/21 + 160/21
x = 307/21 = 14 13/21

7) 4x - 5y = 22|×3|12x - 15y = 66
7x + 3y = 15|×5|35x + 15y = 45
-----------------------------------(+)
47x = 101
x = 101/47
4x - 5y = 22
4.101/47 - 5y = 22
404/47 - 5y = 22
-5y = 22 - 404/47
-5y = 1034/47 - 404/47
-5y = 630/47
y = 630/47 : (-5)
y = 630/47 × (-1/5)
y = -126/47

8) x/4 + y/2 = 7
--------------------(×4)
x + 2y = 28 ... pers(1)
x/2 - y/2 = -4
-----------------(×2)
x - y = -8 .... pers(2)
x + 2y = 28
---------------(-)
-3y = - 36
y = 11
x - y = -8
x - 11 = -8
x = -8 + 11 = 3