Question

Pada sistem persamaan 4x+2y=2 dan 7x+4y=2 tentukan nilai 5x-3y?

Answer 1

4x + 2y = 2 ... (1)
7x + 4y = 2 ... (2)

(2) dikali 2
8x + 4y = 4 ... (1')

(1') - (2)
x = 2

dari (1)
4x + 2y = 2
4(2) + 2y = 2
8 + 2y = 2
2y = -6
y = -3

maka,
5x - 3y = 5(2) - 3(-3)
= 10 - (-9)
= 19

Answer 2

4x+2y=2
7x+4y=2
5x-3y=?
4x+2y=2
2y=2-4x
y=2-4x/2
y=1-2x

7x+4(1-2x)=2
7x+4-8x=2
7x-8x=2-4
-x=-2
x=2

4x+2y=2
4(2)+2y=2
8+2y=2
2y=2-8
2y=-6
y=-6/2
y=-3

5x-3y
=5(2)-3(-3)
=10+9
=19