bonjour
carré 1 = x cm donc aire = x² cm²
carré 2 = x + 2 cm donc aire = x² + 4 x + 4
carré 3 = x + 4 cm donc aire = x² + 8 x + 16
x² + x² + 4 x + 4 + x² + 8 x + 16 = 515
3 x² + 12 x = 515 - 4 - 16
3 x² + 12 x = 495
3 x² + 12 x - 495 = 0
Δ = 144 - 4 ( 3 * - 495 ) = 6 084 = 78 ²
x 1 = ( - 12 + 78 ) / 6 = 11
AB = 11 + 13 + 15 = 39
11 ² + 13 ² + 15 ² = 515
