3x²-5x-1 = 0|:3
x²-5/3x-1/3 = 0
Виет:
{x1+x2 = 5/3
{x1•x2 = -1/3
(x1+x2)² = x1²+2x1x2+x2²
x1²+x2² = (x1+x2)²-2x1x2 = 25/9 + 2/3 = 31/9
3x²-5x-1 = 0|:3
x²-5/3x-1/3 = 0
Виет:
{x1+x2 = 5/3
{x1•x2 = -1/3
(x1+x2)² = x1²+2x1x2+x2²
x1²+x2² = (x1+x2)²-2x1x2 = 25/9 + 2/3 = 31/9