Вправи для повторення розділу 3 » 10

Розв’яжіть рівняння: 1) x2 = 6x – 7; x2 – 6x + 7 = 0; D = (–6)2 – 4 • 7 = 8; x1,2 = (6 ±2√2)/2 = (2(3 ± √2))/2 = 3 ± √2. 2) x2 + 7x = –12; х2 + 7x + 12 = 0; D = 72 – 4 • 12 = 1; х1 = (-7+1)/2 = –3; х2 = (-7-1)/2 = –4. 3) 10x = 25x2 + 1; 25x2 – 10x + 1 = 0; D = (–10)2 – 4 • 25 = 0; х = 10/(2 • 2) = 1/5. 4) 2 – 9х = 5x2; 5x2 + 9х – 2 = 0; D = 92 – 4 • 5 • (–2) = 121; х1 = (-9+11)/10 = 0,2; х2 = (-9-11)/10 = –2.