Bonjour,
selon moi cela donne :
x2 = 81
x = 81/2 = 40,5
x2 = 6,4
x = 6,4/2 = 3,2
x2 = 9
x = 9/2 = 4,5
x2 = 4,9
x = 4,9/2 = 2,45