РОЗДІЛ 4. Квадратні рівняння » 814 (3-5)

3) –3x² – x + 14 = –3(x + 7/3)(x – 2) = –(3x + 7)(x – 2); D = (–1)2 – 4 • (–3) • 14 = 1 + 168 = 169. x1 = (1-√169)/(2•(-3)) = (1-13)/(-6) = (-12)/(-6) = 2; x2 = (1+√169)/(2•(-3)) = (1+13)/(-6) = 14/(-6) = –7/3. 4) 6x² – 5x + 1 = 6(x – 1/2)(x – 1/3) = (2x – 1)(3x – 1); D = (–5)2 – 4 • 6 • 1 = 25 – 24 = 1. x1 = (5-√1)/(2•6) = (5-1)/12 = 4/12 = 1/3; x2 = (5+√1)/(2•6) = (5+1)/12 = 6/12 = 1/2. 5) –9x² + 12x – 4 = –(9x2 – 12x + 4) = –(3x – 2)2;