Répondre :
1.
Soit x-1;x; x+1 les trois nombres
x² - 2x + 1 + x² + x² + 2x + 1 = 13874 => 3x² + 2 = 13874 => 3x² = 13872 => x² = 4624
=> x = 68 ou -68
2.
Volume = 1/3.B.h = 10/3.B = 480 => B = 48.3 = 144
or B = x² => x² = 144 => x = 12
3.
S = 4pi.r² = 628 => r² = 628./4pi = 50 => r = V50 = 5V2 cm
4.
Si OA = 3cm la diagonale est 6cm or la diagonale d'un carré est xV2 = 6cm
donc x = 6/V2 = 3V2cm