Kunci Jawaban Matematika Kelas 9 Halaman 81, Latihan 2.1 Persamaan Kuadrat Nomor 1-5

Soal nomor 4

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