Question

Diketahui sistem persamaan 5x - 2y = -1 dan x - 2y = 3. Nilai dari 2x - 5y adalah
a. 8
b.1
c. -8
d. -12

Answer 1

5x - 2y = -1
  x - 2y = 3    -
4x       = -4
x         = -1

x-2y = 3
-1-2y = 3
-2y = 4
y = -2

2x - 5y= 2(-1) - 5(-2) = -2 +10 = 8 (A)

Answer 2

5x - 2y = -1 dan
x - 2y = 3. => x=2y+3
5x-2y= -1
5(2y+3) - 2y = -1
10y+15 - 2y = -1
8y= -16
y = -2

5x- 2y = -1
5x - 2(-2) = -1
5x +4 = -1
5x= -5
x = -1

2x - 5y
= 2(-1) - 5(-2) 
= -2 +10 = 8