tolong no 2,3 sma no 4

2a) x = y
subtitusi
x + y = 6
y + y = 6
2y = 6
y = 3
subtitusi
x = y
x = 3
hp ( 3,3 )

b) y = 2x
subtitusi
x + 3y = - 21
x + 3(2x) = - 21
x + 6x = - 21
7x = - 21
x = - 3
subtitusi
y = 2x
y = 2(-3)
y = - 6

c) x - 2y = 2
x = 2y + 2
subtitusi
3y - 5x = - 24
3y - 5(2y + 2) = - 24
3y - 10y - 10 = - 24
- 7y = - 24 + 10
- 7y = - 14
y = 2
subtitusi
x - 2y = 2
x - 2(2) = 2
x - 4 = 2
x = 2 + 4
x = 6
hp = ( 6,2 )

d) x + 2y = 0
x = - 2y
subtitusi
2x - 3y = 7
2(-2y) - 3y = 7
- 4y - 3y = 7
- 7y = 7
y = - 1
subtitusi
x + 2y = 0
x + 2(-1) = 0
x - 2 = 0
x = 2
hp = ( 2,-1 )

e) y = 2x
subtitusi
y = - x - 3
2x = - x - 3
2x + x = - 3
3x = - 3
x = - 1
subtitusi
y = 2x
y = 2(-1)
y = - 2
hp = ( - 1 , - 2)

3a) x + y = 10
x - y = 2
-------------------(-)
2y = 8
y = 4
• x + y = 10
x - y = 2
-----------------(+)
2x = 12
x = 6
hp = ( 6,4 )

b) x + 2y = 3
x + 3y = 4
------------------(-)
- y = - 1
y = 1
• x + 2y = 3 |×3
x + 3y = 4 |×2
maka
3x + 6y = 9
2x + 6y = 8
-----------------(-)
x = 1
hp = ( 1 , 1 )

c) 2x + y = 5 |×2
3x - 2y = 11
maka
4x + 2y = 10
3x - 2y = 11
------------------(+)
7x = 21
x = 3
• 2x + y = 5 |×3
3x - 2y = 11 |×2
maka
6x + 3y = 15
6x - 4y = 22
--------------------(-)
7y = - 7
y = - 1
hp = ( 3,-1 )

d) 2x + y - 8 = 0
2x + y = 8
3x + 2y - 7 = 0
3x + 2y = 7
• 2x + y = 8 |×2
3x + 2y = 7
maka
4x + 2y = 16
3x + 2y = 7
------------------(-)
x = 9
• 2x + y = 8 |×3
3x + 2y = 7 |×2
maka
6x + 3y = 24
6x + 4y = 14
-------------------(-)
- y = 10
y = - 10
hp = ( 9, - 10)

e) 4x = 3y
4x - 3y = 0
2x - 3y = - 6
------------------(-)
2x = 6
x = 3
• 4x - 3y = 0
2x - 3y = - 6 |×2
maka
4x - 3y = 0
4x - 6y = - 12
--------------------(-)
3y = 12
y = 4
hp = ( 3,4 )

3a) 4x - 5y = - 12
2x + 3y = 16 |×2
maka
4x - 5y = - 12
4x + 6y = 32
-------------------(-)
- 11y = - 44
y = 4
subtitusi
2x + 3y = 16
2x + 3(4) = 16
2x + 12 = 16
2x = 16 - 12
2x = 4
x = 2
hp = ( 2,4 )