Kunci Jawaban Matematika Kelas 9 Semester 1 Halaman 129 dan 130 Uji Kompetensi 2 Fungsi Kuadrat

Soal nomor 4

Diketahui (1 – m)x2 + (8 – 2m)x + 12 = 0, maka:

a = 1 – m
b = 8 – 2m
c = 12

D = b2 – 4ac
(8 – 2m)2 – 4(1-m)(12) = 0
64 – 32m + 4m2 – 48 + 48m = 0
4m2 + 16m + 16 = 0
m2 + 4m + 4 = 0
(m + 2)(m + 2) = 0
m + 2 = 0
m = -2

Jadi nilai m adalah -2

Baca juga: Kunci Jawaban Bahasa Indonesia Kelas 8 Halaman 30 Kurikulum Merdeka: Menentukan Tanda Baca

Soal nomor 5

D = 121
D = b2 – 4ac
121 = (-92) – 4 2c
121 = 81 – 8c
8c = 81 – 121
8c = - 40
c = -5

Jadi nilai c adalah -5

Soal nomor 6

a + b = 12
a = 12 – b
a.b = 35

(12 – b) b = 35
-b2 + 12b – 35 = 0
(b – 7) (b – 5) = 0
b = 7, b = 5

a = 12 – b
a = 12 – 7
a = 5
dan
a = 12 – b
a = 12 – 5
a = 7

Jadi, bilangan cacah yang dimaksud adalah 5 dan 7

Soal nomor 7

x2 −2x + 7 = 0 maka, a = 1, b = -2, c = 7
x1 + x2 = -b/a
x1 + x2 = -(-2)/1
x1 + x2 = 2