Question

Diketahui sistem persamaan 3x + 4y = 8 dan -2x + 7 = -16 nilai 2x - 7y adalah

Answer 1

-2x + 7 = -16
-2x = -16-7
-2x = -23
x = 23/2

3x+4y = 8
3(23/2) + 4y = 8
69/2 + 4y = 8
69/2 - 8 = -4y
(69-16)/2 = -4y
53/2 = -4y
-53/8 = y

2x - 7y
2 ( 23/2) - 7 (-53/8)
23 + 371/8
(184+371)/8
555/8
69 3/8

Answer 2

Dik: -2x + 7 = -16
       3x + 4y = 8

Dit: 2x - 7y = ...?
Jawab;
-2x + 7 = -16
-2x = -16 - 7
-2x = -23
x = 
x = 11,5

3x + 4y = 8
3.(11,5) + 4y = 8
4y = 8 - 34,5
4y = -26,5
y = 
y = - 6,625

2x - 7y = 2.(11,5) - 7.(6,625)
            = 23 - 46,375
            = -23,375

JADI, nilai 2x - 7y adalah -23,375