Kunci Jawaban Matematika Kelas 9 SMP Halaman 81-82, Latihan 2.1 Materi Persamaan Kuadrat, Semester 1

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

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

7. 3x2 = 2x – 4
Maka 3x2 – 2x + 4 = 0

8. (a) 

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

8. (b)

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

8. (c)

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

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

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