x² = (x-40)²+(x-20)²
x² = x² - 80x + 1600 + x² - 40x + 400
0 = - 120x + 2000 + x²
x² - 120x + 2000 = 0
Astuce !!!! look
x² - 20x - 100x + 2000 = 0
x (x - 20) - 100(x - 20) = 0
x (x - 20) - 100(x - 20) = 0
(x - 20) ( x - 100) = 0
Solution S = { 20, 100)
