РОЗДІЛ 4. Квадратні рівняння » 812 (5-8)

5) –x² + 4x – 3 = –(x – 1)(x – 3); D = 42 – 4 • (–1) • (–3) = 16 – 12 = 4. x1 = (-4-√4)/(2•(-1() = (-4-2)/(-2) = (-6)/(-2) = 3; x2 = (-4+√4)/(2•(-1)) = (-4+2)/(-2) = (-2)/(-2) = 1. 6) x² – 6x – 7 = (x + 1)(x – 7); D = (–6)2 – 4 • 1 • (–7) = 36 + 28 = 64. x1 = (6-√64)/(2•1) = (6-8)/2 = (-2)/2 = –1; x2 = (6+√64)/(2•1) = (6+8)/2 = 14/2 = 7. 7) x² + 4x + 4 = (x + 2)2; 8) –x² + 10x – 25 = –(x² – 10x + 25) = –(x – 5)².