\(b,\frac{1978\cdot1979+1980\cdot21+1958}{1980\cdot1979-1978\cdot1979}\\ =\frac{1978\cdot1979+\left(1979+1\right)\cdot21+1958}{1979\left(1980-1978\right)}\\ =\frac{1978\cdot1979+1979\cdot21+\left(21+1958\right)}{1979\cdot2}\\ =\frac{1978\cdot1979+1979\cdot21+1979}{1979\cdot2}\\ =\frac{1979\left(1978+21+1\right)}{1979\cdot2}\\ =\frac{2000}{2}\\ =1000\)

\(\frac{1978.1979+1980.21+1958}{1980.1979-1978.1979}=\frac{1978.1979+1979.21+21+1958}{1979\left(1980-1978\right)}=\frac{1979.1978+1979.21+1979}{1979.2}=\frac{1979\left(1978+21+1\right)}{1979.2}=\frac{2000}{2}=1000\)

Nhớ tick và theo dõi mik nhá!

222222222222222222222

=1001 nkaq bn 

mk nka

\(\frac{1978.1979+1980.21+1958}{1980.1979-1978.1979}\)

\(=\frac{1978.1979+1979.21+21+1958}{1979.\left(1980-1978\right)}\)

\(=\frac{1979.\left(1978+21\right)+21+1958}{1979.2}\)

\(=\frac{1979.\left(1978+21+1\right)}{1979.2}\)

\(=\frac{1979.2000}{1979.2}\)

\(=\frac{2000}{2}\)

\(=1000\)

ai trả lời dùm mình đi

1980.1979-1978.1979

=1979.(1980-1978)

=1979.2

=3958

Đơn giản : 

Ta có :\(\frac{1978.1979+1980.21+1958}{1980.1979-1978.1979}\)

\(=\frac{1978.1979+1979.21+21+1958}{1979\left(1980-1978\right)}\)

\(=\frac{1978.1979+1979.21+1979}{1979.2}\)

\(=\frac{1979.\left(1978+21+1\right)}{1979.2}\)

\(=\frac{2000}{2}=1000\)

cái này cx dễ ợt!tự động não nhóe

thế tính nhanh cho tui