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\(b,\frac{1978\cdot1979+1980\cdot21+1958}{1980\cdot1979-1978\cdot1979}\\ =\frac{1978\cdot1979+\left(1979+1\right)\cdot21+1958}{1979\left(1980-1978\right)}\\ =\frac{1978\cdot1979+1979\cdot21+\left(21+1958\right)}{1979\cdot2}\\ =\frac{1978\cdot1979+1979\cdot21+1979}{1979\cdot2}\\ =\frac{1979\left(1978+21+1\right)}{1979\cdot2}\\ =\frac{2000}{2}\\ =1000\)
\(\frac{1978.1979+1980.21+1958}{1980.1979-1978.1979}\)
\(=\frac{1978.1979+1979.21+21+1958}{1979.\left(1980-1978\right)}\)
\(=\frac{1979.\left(1978+21\right)+21+1958}{1979.2}\)
\(=\frac{1979.\left(1978+21+1\right)}{1979.2}\)
\(=\frac{1979.2000}{1979.2}\)
\(=\frac{2000}{2}\)
\(=1000\)
Đơn giản :
Ta có :\(\frac{1978.1979+1980.21+1958}{1980.1979-1978.1979}\)
\(=\frac{1978.1979+1979.21+21+1958}{1979\left(1980-1978\right)}\)
\(=\frac{1978.1979+1979.21+1979}{1979.2}\)
\(=\frac{1979.\left(1978+21+1\right)}{1979.2}\)
\(=\frac{2000}{2}=1000\)
(1979.1979+1980.21+1958):(1980.1979-1978.1979)
=(1979.1979+1980.21+1958):(1979.(1980-1878))
=(1979.1979+1980.21+1958):(1979.2)
=(1980.21+1958)+(1979.1979):(1979.2)
=1980.21+1958
=41580+1958
=43538
(1979.1979+1980.21+1958):(1980.1979-1978.1979)
=(1979.1979+1980.21+1958):(1979.(1980-1878))
=(1979.1979+1980.21+1958):(1979.2)
=(1980.21+1958)+(1979.1979):(1979.2)
=1980.21+1958
=41580+1958
=43538