Tính nhanh: 1 0 \(\large\dfrac{1}{1997}\) \(\large\dfrac{1}{1994}\) \(

Tính nhanh:

• A.

  1

• B.

  0

• C.

  \(\large\dfrac{1}{1997}\)

• D.

  \(\large\dfrac{1}{1994}\)

\(\large\dfrac{1995}{1997}\times\dfrac{1990}{1993}\times\dfrac{997}{995}\times\dfrac{1993}{1995}\times\dfrac{1997}{1994}\)
\(\large =\dfrac{1995\times 1990 \times 997 \times 1993 \times 1997}{1997\times 1993 \times 995 \times 1995 \times 1994}\)
\(\large =\dfrac{1990 \times 997}{995 \times 1995 \times 1994} = \dfrac{995 \times 2 \times 997}{995 \times 997 \times 2} = 1\)