Розділ 3. КВАДРАТНІ РІВНЯННЯ » 24.10 (4-6)

4) –x² + x + 12. D = 1² – 4 • (–1) • 12 = 49; x1 = (-1+7)/(-2 ) = –3; x2 = (-1-7)/(-2) = 4; –x² + x + 12 = –(x + 3)(х – 4) = (x + 3)(4 – x). 5) –6x² – 5x + 1. D = (–5)² – 4 • (–6) = 49; x1 = (5+7)/(-12) = –1; x2 = (5-7)/(-12) = 1/6; –6x² – 5x + 1 = –6(x + 1)(x – 1/6) = (x + 1)(1 – 6x). 6) 7x² + 19x – 6. D = 19² – 4 • 7 • (–6) = 529; √D = 23; x1 = (-19+23)/(2 • 7) = 2/7; x2 = (-19-23)/(2 • 7) = –3; 7x² + 19x – 6 = 7(x – 2/7)(x + 3) = (7x – 2)(x + 3).