Fie ecuatia: x²-2x-9=0, aflati valoarea sumei: x1²+x2². Dau coroana!

Răspuns :

x² - 2x - 9 = 0

Δ = 4 - 4×1×(-9) = 4 + 36 = 40

x1 = (2 + 2√10) / 2 = 2(1 + √10)/2 = 1 + √10

x2 = (2 - 2√10)/2 = 2(1 - √10) / 2 = 1 - √10

(x1)² + (x2)² =

(1+√10)² + (1 -√10)² =

1 + 2√10 + 10 + 1 - 2√10 + 10 =

22