Dibutuhkan Help untuk No. 1-5 :)) Makasih yang mo bantuin. Kalo gaada yang mo bantuin gapapasi.

Bab Persamaan Garis
Matematika SMP Kelas VIII

1]
2x + y = 18
x - y = 6
------------------- +
3x = 24
x = 8

x - y = 6
8 - 6 = y
y = 2

x = 8 dan y = 2

2] (1/3) x - y = -3
✩✩ dikali 3 ✩✩
x - 3y = -9
x = 3y - 9

x + (1/2) y = 5
✩✩ dikali 2 ✩✩
2x + y = 10
2(3y - 9) + y = 10
6y - 18 + y = 10
7y = 10 + 18
y = 28/7
y = 4

x = 3y - 9
x = 3 . 4 - 9
x = 12 - 9
x = 3

x = 3 dan y = 4

3] motor = a
mobil = b

2a + 4b = 210
a + 2b = 105

a + 2b = 105
a + b = 75
----------------- -
b = 30

a + b = 75
a + 30 = 75
a = 75 - 30
a = 45

Pendapatan
= 4.000 . 30 + 2.000 . 45
= 120.000 + 90.000
= Rp 210.000,00

4] p = 10 + l

keliling = 60
2 . (p + l) = 60
10 + l + l = 60/2
2l = 30 - 10
l = 20/2
l = 10 cm

5] x² - 4y² = 9
x² = 4y² + 9

4x² - 2y² = 92
4 (4y² + 9) - 2y² = 92
16y² + 36 - 2y² = 92
14y² = 92 - 36
y² = 56/14
y = √4
y = +- 2

x² = 4y² + 9
x² = 4 . (2)² + 9
x² = 4 . 4 + 9
x = √(16 + 9)
x = √25
x = +- 5

x² = 4y² + 9
x² = 4 . (-2)² + 9
x = 4 . 4 + 9
x = √(16 + 9)
x = √25
x = +- 5

Maka, (-2, -5), (-2, 5), (2, -5), (2, 5)

# terima kasih untuk pak newwiguna