A) 1 1 2 16 66 2 6 2X 7 6 6 7 2X 6 71 1313...
Bài 9: a) 1 1 2 16 66 2 6 2x 7 6 6 7 2x 6 71 1313 2x 1 13 2x 1 2 x 2 . Vậy 1 13S x x 2 2 x x x b) 1 2 1 1 2 43x x 3