Question

Penyelesaian dari sistem persamaan 2x - 5y =-16 dan 5x + 2y = -11 adalah x dan y . nilai 5x - 9y adalah

Answer 1

2x - 5y = -16 | ×2
5x + 2y = -11 | ×5

4x - 10y = -32
25x + 10y = -55
------------- +
29x = -87
x = -3

5(-3) + 2y = -11
-15 + 2y = -11
2y = -11 + 15
2y = 4
y = 2

5x - 9y
5(-3) - 9(2)
-15 - 18 = -33

Answer 2

2x - 5y = -16  | x5 | 10x - 25y = -80 
5x + 2y = -11 | x2 | 10x + 4y  = -22  -
                                   -29y = -58
                                         y = -58/-29 = 2
2x - 5y = -16
2x - 5(2) = -16
2x - 10 = -16
2x = -16 + 10
2x = -6
x = -6/2 = -3

5x - 9y =
5(-3) - 9(2) =
-15 - 18 = -33