a. x² - 1 = 0
x² - 1 = (x + 1) (x - 1)
Maka x = 1 atau x = -1.

b. 4x² + 4x + 1 = 0
4x² + 4x + 1 = 0
(2x + 1 ) (2x + 1) = 0
Maka x = -1/2

c. -3x - 5x +2 = 0
3x + 5x - 2 = 0
(3x - 1) (x + 2) = 0
Maka x = 3x - 1 atau x = ⅓
x = x + 2 atau x = -2

d. 2x² - x - 3 = 0
(2x - 3) (x + 1) = 0
2x - 3 = 0 atau x + 1 = 0
Maka x = 3/2 atau x = -1

e. x² - x + ¼ = 0
(x - ½) (x - ½) = 0
Maka x = ½

Soal nomor 5

a. a. 3x² – 12 = 0
3x² – 12 = 0
Maka a = 3, b = 0, c = -12
Jadi Diskiriminan = 0² – 4(3)(–12) = 144

b. x² + 7x + 6 = 0
x² + 7x + 6 = 0
Maka a = 1, b = 7, c = 6
Jadi Diskiriminan = 7² – 4(1)(6) = 49 – 24 = 25

c. -3x² - 5x + 2 = 0
-3x² - 5x + 2 = 0
Maka a = -3, b = -5, c = 2

Jadi Diskiriminan = (–5)² – 4(–3)(2) = 25 + 24 = 49

Soal nomor 6

3x² – 5x + c = 0
Maka a = 3, b = -5

Jika D = b² - 4ac, D = 49
49 = (-5)² - 4.3.c
49 - 25 = -12.c
-12.c = 24
c = - 24/12
c = - 2

Soal nomor 7

3x² = 2x – 4
Maka 3x² – 2x + 4 = 0

Soal nomor 8

a. x² – 5x + 6 = 0
x – 3 = 0 dan x – 2 = 0
Maka x = 3 atau x = 2

b. b. x² + 2x – 15 = 0
x + 5 = 0 dan x - 3 = 0
Maka x = -5 atau x = 3

c. x^2 + 4x – 12 = 0
x + 6 = 0 dan x - 2 = 0
Maka x = -6 atau x = 2

Soal nomor 9

α = 2 dan β = 5
(X + α) . (x + β)
(x + 2 )(x + 5) = 0
x² + 5x + 2x + 10
Maka persamaan kuadratnya menjadi x² + 7x + 10

Soal nomor 10

2(x^2 + 1) = x(x + 3)
2x^2 + 2 = x^2 + 3x
2x^2 - x^2 – 3x + 2 = 0
x^2 – 3x + 2 = 0

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Baca Juga: Kunci Jawaban Matematika Kelas 9 Halaman 55 56 Kurikulum Merdeka