5x+2y=-3 7x+8y=1 maka nilai x-y

Bab Persamaan Linear
Matematika SMP Kelas VIII

5x + 2y = - 3 → dikali 4 → 20x + 8y = - 12

20x + 8y = -12
  7x + 8y =    1
-------------------- -
       13x = -13
          x = - 1

5x + 2y = - 3
5 . (-1) + 2y = -3
2y = -3 + 5
y = 2/2
y = 1

x - y = -1 - 1
         = -2

5x + 2y = -3 (× 4)
7x + 8y = 1 (× 1)

20x + 8y = -12
...7x + 8y = ...1
---------------------- -
13x...........= -13
x = -13/13
x = -1

5x + 2y = -3
5(-1) + 2y = -3
-5 + 2y = -3
2y = -3 + 5
2y = 2
y = 2/2
y = 1


nilai x - y = -1 - 1 = -2

Jadi nilai x - y adalah -2