Bonjour,
Un = 2n² - n + 1
1) Uo = 2 × 0² - 0 + 1 = 1
U1 = 2 × 1² - 1 + 1 = 2
U2 = 2 × 2² - 2 + 1 = 8 - 2 + 1 = 7
2) U5 = 2 × 5² - 6 + 1 = 2 × 25 - 5 + 1 = 50 - 5+ 1 = 46
3) U(n+1) = 2(n+1)² - (n + 1) + 1 = 2n² + 4n + 2 - n - 1 + 1 = 2n² + 3n + 2
U(n-1) = 2(n-1)² - (n-1) + 1 = 2n² - 4n + 2 - n + 1 + 1 = 2n² - 5n + 4
→ tu termines ?
