( 42-2,05x)²=( 1,05x)²+x²

(42-2,05x)² = (1,05x)² + x² 1764 - 2422,05x + (2,05x)² = 1,1025x² + x² 1764 - 172,2x + 4,2025x² = 1,1025x² + x² 1764 - 172,2x + 4,2025x² = 2,1025x² 0,0025x² - 172,2x + 1764 = 0