Đáp án:
Giải thích các bước giải:
a) $A = (1 - \frac{1}{10} ) (1 - \frac{1}{11} ) \times ... \times (1 - \frac{1}{2003} ) \\\Leftrightarrow A = \frac{9}{10} \times \frac{10}{11} \times \frac{11}{12} \times ... \times \frac{2004}{2003} \\\Leftrightarrow A = \frac{9}{2003} $
b) $B = 50,75 - 48,25 + 46,75 - 44,25 + ... + 6,75 - 4,25 + 2,75 \\\Leftrightarrow B = (2 + 6 + ... + 50 + 12 \times \frac{3}{4} ) - (4 + 8+ ... + 48 + 13 \times \frac{1}{4} ) \\\Leftrightarrow B = (2 + 6 +... + 50) - (4 + 8 + ... + 48) + \frac{23}{4} \\\Leftrightarrow B = 4 ( \frac{13 ^ 2}{2} + \frac{13}{2} ) - 2 \times 13 - 4 ( \frac{12 ^ 2}{2} + \frac{12}{2} ) \\\Leftrightarrow B = \frac{131}{4} $
