Diketahui persamaan 2x-5y+12=0 dan 5x-2y=0 nilai 3x-4y adalah

Kelas 8 Matematika
Bab Persamaan Garis

2x - 5y + 12 = 0 → dikali 5 → 10x - 25y + 60 = 0
5x - 2y + 9 = 0 → dikali 2 → 10x - 4y + 18 = 0

10x - 25y = -60
10x - 4y = -18
----------------------- -
-21y = -42
y = 2

2x - 5y + 12 = 0
2x - 5 . 2 + 12 = 0
2x = -2
x = -1

3x - 4y 
= 3 . (-1) - 4 . 2
= -3 - 8
= -11

Kelas 8 Matematika
Bab SPLDV

2x - 5y + 12 = 0 → dikali 5 → 10x - 25y + 60 = 0
5x - 2y = 0 → dikali 2 → 10x - 4y = 0

10x - 25y + 60 = 0
10x - 4y = 0
--------------------------- -
-21y = 60
y = 60/-21
y = -20/7

5x - 2y = 0
5x - 2 . (-20/7) = 0
5x = -40/7
x = -8/7

3x - 4y
= 3 . (-8/7) - 4 . (-20/7)
= -24/7 + 80/7
= 56/7
= 8