Question

 tính nhanh 1994x1993-1992x1993/1992x1993+1994x7+1986

Answer 1

\(=\dfrac{1994.1993-1992.1993}{1992.1993+1994.7+1986}=\dfrac{1993.\left(1994-1992\right)}{1992.1993+1992.7+2.7+1986}\)

\(=\dfrac{2.1993}{1992.\left(1993+7\right)+14+1986}=\dfrac{2.1993}{1992.2000+2000}=\dfrac{2.1993}{\left(1992+1\right).2000}\)

\(=\dfrac{2.1993}{1993.2000}=\dfrac{2}{2000}=\dfrac{1}{1000}\)