Je vais noter sqrt la racine carré:
B = sqrt(81 x 36) - 11 x sqrt(2) x sqrt(8) -9
= sqrt(9x9 x 6x6) - 11 x sqrt(2) x sqrt(4x2) -9
= sqrt(9x9) x sqrt(6x6) - 11 x sqrt(2) x sqrt(4) x sqrt(2) - 9
= 9 x 6 - 11 x sqrt(2) x 2 x sqrt(2) - 9
= 54 - 22 x 2 x sqrt(2) x sqrt(2) - 9
= 54 - 88 - 9
= - 42