tolong di bantu soalnya susah nomor 14 15

14.
[tex] \frac{1}{3} x - \frac{2}{5} y = 3 \: \: \: dua \: ruas \: kali \: 15 \\ 5x - 6y = 45[/tex]
[tex] \frac{2}{3} x + \frac{1}{5} y = 1 \: dua \: ruas \: kali \: 15 \\ 10x + 3y = 15[/tex]
Eliminasi :
5x - 6y = 45 | *2
10x + 3y = 1 |*1
.....................
10x - 12y = 90
10x + 3y = 1
...................... -
-15y = 75
y = 75/-15
y = -5

Tentukan nilai x :
5x - 6y = 45
5x - 6(-5) = 45
5x + 30 = 45
5x = 45-30
5x = 15
x = 15/5
x = 3

Maka :
x = m = 3
y = n = -5

Sehingga, 2m - 2n :
= 2(3) - 2(-5)
= 6 - (-10)
= 16

Jawaban B.




15.
[tex]2x - 6 \geqslant 18 + 4x \\ 2x - 4x \geqslant 18 + 6 \\ - 2x \geqslant 24 \\ x \leqslant - \frac{24}{2} \\ x\leqslant - 12[/tex]
HP {..., -15,-14,-13,-12}

Jawaban C