Відповіді §.11 - §.12 » §.12 (2.3-4)

3) у = –х2 + bx + c. M(–2; 15) N(3; –20). 15 = –4 – 2b + c. –20 = –9 + 3b + c. c – 2b = 19. c + 3b = –11. –5b = 30. b = –6. c = 2b + 19 = –12 + 19 = 7. y = –x2 – 6x + 7. a = –1 < 0 вітки вниз. хв = –b/2a = 6/(-2) = –3. ув = –9 + 18 + 7 = 16. (–3; 16) – вершина. 4) у = ах2 + bx + c. M(0; 40) N(1; 26) K(–1; 58) 40 = c y = ax2 + bx + 40. 26 = a + b + 40. 58 = a – b + 40. a + b = –14. a – b = 18. 2a = 4. a = 2. b = –14 – 2 = –16. y = 2x2 – 16x + 40. x = 2 > 0 ∪ хв = –b/2a = 16/4 = 4. ув = 2 • 16 – 16 • 4 + 40 = 32 – 64 + 40 = 8. (4; 8) – вершина.