Dik: Persamaan =2x -5y+12=0 dan 5x -2y+9=0 Dit: Nilai 3x - 4y A.14 B.11 C.-11 D.-14

Jawabannya:

2x-5y=12 |×2|
5x-2y=9 |×5|

4x-10y= 24
25x-10y= 45
----------------- -
-21x = -21
x = -21/-21
x = 1

2x-5y= 12 |×5|
5x-2y= 9 |×2|

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

Maka:
3x-4y
= 3(-1) - 4(2)
= -3 - 8
= -11 → Opsi C

# Semoga Membantu
Mohon dikoreksi lagi

Pakai cara eliminasi
2x - 5y + 12 = 0
2x - 5y = -12 (dikali 5)

5x - 2y + 9 = 0
5x - 2y = -9 (dikali 2)

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

2x - 5y = -12
2x - 5(2) = -12
2x - 10 = -12
2x = -12 + 10
x = -1

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

jawabannya yang c