diketahui persamaan 2x - 5y + 12 =0 dan 5x - 2y + 9 =0. nilai 3x - 4y adalah

[tex]2x - 5y + 12 = 0 \\ 2x - 5y = - 12...( \times 5) \\ 10x - 25y = - 60 \\ \\ 5x - 2y + 9 = 0 \\ 5x - 2y = - 9...( \times 2) \\ 10x - 4y = - 18 \\ \\ 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[/tex]

2x - 5y = -12 )×5
5x - 2y = -9 )×2

10x - 25y = -60
10x - 4y = -18
___________ -
-21y = -42
y = 2
2x-5y = -12
2x-5.2 = -12
2x = -2
x = -1

3x-4y = 3.-1 - 4.2 = -3 - 8 = -11