Question

Jika 4x + 3y = 30 dan 3x + 2y = 25 maka x + y =.....

Answer 1

4x + 3y = 30.............. (1)
3x + 2y = 25...............(2) jika di kurangi menjadi
x + y = 5.......................(3)
x = 5 - y........................(4)

masukkan persamaan 4 ke persamaan 1

4 (5-y) + 3y = 30
20 - 4y + 3y = 30
-y = 30 - 20
-y = 10
y = -10

x = 5-y
= 5 - (-10)
= 5 + 10
x = 15

x + y = 15 - 10 = 5