Baca Juga: Makna Alenia Pertama Pembukaan UUD 1945, Kunci Jawaban PKN Kelas 9 SMP Halaman 51
Jawaban: y = -D/4a = -(b2 – 4ac)/4a = -((7)2 – 4(-3/4)(-18))/4(-3/4) = -(49 – 54)/-3 = -5/3.
3. Sketsalah grafik fungsi berikut ini.
a. y = 2x2 + 9x.
Jawaban: y = 0 → 2x2 + 9x = 0 → 0 = x(2x + 9) → 2x + 9 = 0 → 2x = -9 → x = -4,5.
Titik puncak = (-b/2a, (b2 – 4ac)/4a) → (-(9)/(2.2), (92 – 4)/4) → (-2,25, -10,125).
b. y = 8x2 – 16x + 16.
Jawaban: y = 0 → 0 = 8x2 + 16x + 6 → (-b ± √b2 – 4ac)/2a → (16 ± √256 – 192)/16 → (16 ± 8) /16.