Kunci Jawaban Matematika Kelas 9 Halaman 81 82 Latihan 2.1 Akar Persamaan Kuadrat: Dilengkapi Pembahasan Cara

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

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

Baca Juga: Kunci Jawaban IPA Kelas 9 Halaman 103 104 Lengkapilah Tabel 2.10 Metamorfosis Sempurna dan Tidak Sempurna

c. –3x² – 5x + 2 = 0
a = -3, b = -5, c = 2
x₁₂ = [(-b ± √(b² - 4ac)]/2a
x₁₂ = [-(-5) ± √((-5)² - 4(-3)(2))]/2(-3)
x₁₂ = [(5) ± √(25 - (-24))]/-6
x₁₂ = [(5) ± √(49)]/-6
x₁₂ = [(5) ± 7]/-6
x₁ = [(5) + 7]/-6 = 12/-6 = -2
x₂ = [(5) - 7]/-6 = -2/-6 = ⅓

d. 2x² – x – 3 = 0
a = 2, b = -1, c = -3
x₁₂ = [(-b ± √(b² - 4ac)]/2a
x₁₂ = [-(-1) ± √((-1)² - 4(2)(-3))]/2(2)
x₁₂ = [(1) ± √(1 + 24)]/4
x₁₂ = [(1) ± √(25)]/4
x₁₂ = [(1) ± 5]/4
x₁ = [(1) + 5]/4 = 6/4 = 3/2
x₂ = [(1) - 5]/4 = -4/4 = -1

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

Baca Juga: Kunci Jawaban IPA Kelas 9 Halaman 77 78 Gambar 2.27 Perkembangan Hidup Tumbuhan Angiospermae Proses - Struktur

5. Tentukan nilai diskriminan persamaan pada soal no. 1

Rumus diskriminan D = b² – 4ac
a. 3x² – 12 = 0
a = 3, b = 0, c = -12
D = 0² – 4(3)(-12)
D = 0 – (-144) = 144

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