(x - 5)² = 5x² - (2x - 1)(2x + 1)
x² - 10x + 25 = 5x² - 4x² + 1
x² - 10x + 25 = x² + 1
x² - 10x - x² = 1 - 25
- 10x = - 24
x = 2,4
<span>(2x-1)²=3x²-4x+17</span>
х²+6х+11=(х²+2*3*х+3²)+2=(х+3)²+2.
(а²+2*а*в+в²)=(а+в)²