РОЗДІЛ 4. Квадратні рівняння » 787 (1-8)

787. Скориставшись теоремою Вієта, розв’яжіть квадратне рівняння: 1) x2 + 3x – 4 = 0. x1 + x2 = –3; x1 • x2 = –4; x1 = –4; x2 = 1. 2) x2 – 6x – 16 = 0. x1 + x2 = 6; x1 • x2 = –16; x1 = –2; x2 = 8. 3) x2 + 7x – 30 = 0 x1 + x2 = –7; x1 • x2 = –30; x1 = 3; x2 = –10. 4) x2 – 10x + 16 = 0. x1 + x2 = 10; x1 • x2 = 16; x1 = 2; x2 = 8. 5) x2 – 12x + 11 = 0. x1 + x2 = 12; x1 • x2 = 11. x1 = 1; x2 = 11. 6) x2 – 9x + 8 = 0. x1 + x2 = 9; x1 • x2 = 8. x1 = 1; x2 = 8. 7) x2 + x – 12 = 0. x1 + x2 = –1; x1 • x2 = –12. x1 = –4; x2 = 3. 8) x2 – 15x + 26 = 0; x1 + x2 = 15; x1 • x2 = 26. x1 = 2; x2 = 13.