dgn jalannya jgn asal asalan

20.)
y = x² (i) ,, y = x + 6 (ii)

Persamaan i dan ii digabung
x² = x + 6
x² - x - 6 = 0
(x - 3)(x + 2) = 0
x = 3 atau x = -2

utk x = 3
y = 3² , y = 9

utk x = 2
y = 2² , y = 4

HP :{((-2 , 4) ; (3 , 9)} B

______________________________

21.)
x² - 5x - y + 4 = 0 (i)

x - 4y = 1 , x = 1 + 4y (ii)

Subs. persamaan ii ke i

(1 + 4y)² - 5(1 + 4y) - y + 4 = 0
16y² + 8y + 1 - 5 - 20y - y + 4 = 0
16y² - 13y = 0
y(16y - 13) = 0
y = 0 atau y =13/16

Utk y = 0
x - 4(0) = 1
x = 1

Utk y =13/16
x - 4(13/16) = 1
x = 1 + 13/4
x = 17/4

HP :{(1 , 0) ; (17/4 , 13/16)} D

__________________________

22.)
y = 8x - x² (i)
3y = x² (ii)

subs. Pers. (i) ke (ii)
3(8x - x²) = x²
24x - 3x² = x²
4x² -24x = 0
4x(x - 6) = 0
x = 0 atau x = 6

Utk x = 0
y = 8(0) - 0²
y = 0

Utk x = 6
y = 8(6) - 6²
y = 12

HP:{(0 , 0) ; (6 , 12)} B