Question

1 1/5 x 1 1/6x 1 1/7 x...x1 1/2006

1 1/3x 1 1/8 x 1 1/15x ... 11/9

(1-1/2)x(1-1/3)x(1-1/4)x...x(1-1/2600)

giúp mình nha mình can gấp lắm

Answer 1

1. \(1\frac{1}{5}x1\frac{1}{6}x1\frac{1}{7}x...x1\frac{1}{2006}\)

\(=\frac{6}{5}x\frac{7}{6}x\frac{8}{7}x...x\frac{2007}{2006}\)

\(=\frac{6x7x8x...x2007}{5x6x7x...x2006}\)

\(=\frac{2007}{5}.\)

2. Câu này đề chắc chắn sai.

3.\(\left(1-\frac{1}{2}\right)x\left(1-\frac{1}{3}\right)x\left(1-\frac{1}{4}\right)x...x\left(1-\frac{1}{2600}\right)\)

\(=\frac{1}{2}x\frac{2}{3}x\frac{3}{4}x...x\frac{2599}{2600}\)

\(=\frac{1x2x3x...x2599}{2x3x4x...x2600}\)

\(=\frac{1}{2006}.\)