A) A = 5 5 7 11 11 1 5 7 11      .5 1 11

Câu 1: a) A = ^{5 5 7 11 11 1} 5 7 11

     

5 1 11



b) B = 5 ^{5 5 11} 5 11

  .



5

Vậy A - B = 5 7   11  5  11 = 7, đpcm.