Kunci Jawaban Matematika Kelas 9 Halaman 81 dan 82, Soal Nomor 1 - 10

Soal nomor 4

a. x⊃2; - 1 = 0
x⊃2; - 1 = (x + 1) (x - 1)
Maka x = 1 atau x = -1.

b. 4x⊃2; + 4x + 1 = 0
4x⊃2; + 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. 2x⊃2; - x - 3 = 0
(2x - 3) (x + 1) = 0
2x - 3 = 0 atau x + 1 = 0
Maka x = 3/2 atau x = -1

e. x⊃2; - x + ¼ = 0
(x - ½) (x - ½) = 0
Maka x = ½

Soal nomor 5

a. a. 3x⊃2; – 12 = 0
3x⊃2; – 12 = 0
Maka a = 3, b = 0, c = -12
Jadi Diskiriminan = 0⊃2; – 4(3)(–12) = 144

b. x⊃2; + 7x + 6 = 0
x⊃2; + 7x + 6 = 0
Maka a = 1, b = 7, c = 6
Jadi Diskiriminan = 7⊃2; – 4(1)(6) = 49 – 24 = 25

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

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

Soal nomor 6

3x⊃2; – 5x + c = 0
Maka a = 3, b = -5

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

Soal nomor 7