\(\frac{1978\times1979+1980\times21+1958}{1980\times1979-1978\times1979}=\frac{1979\times1978+\left(1979+1\right)\times21+1958}{1979\times\left(1980-1978\right)}\)

\(=\frac{1979\times1978+1979\times21+21+1958}{1979\times2}=\frac{1979\times\left(1978+21+1\right)}{1979\times2}\)

\(=\frac{1979\times2000}{1979\times2}=1000\)

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

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

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

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

= \(\frac{1978+21+1}{2}\)

= \(\frac{2000}{2}\)= 1000

=1979x1978+1979x21+21+1958/1979x(1980-1978)

=1979x1979+1979/1979x2

=1979x1980/1979x2

=1979x2x990/1979x2

=990 chúc bạn học tốt nha

=1979x1978+1979x21+21+1958/1979x(1980-1978)

=1979x1979+1979/1979x2

=1979x1980/1979x2

=1979x2x990/1979x2

=990

\(=\frac{1978x1979+\left(1979+1\right)x21+1958}{1979x\left(1980-1978\right)}\)

\(=\frac{1978x1979+1979x21+21+1958}{1979x2}\)

\(=\frac{1978x1979+1979x21+1979}{1979x2}\)

\(=\frac{1979x\left(1978+21+1\right)}{1979x2}\)

\(=\frac{2000}{2}\)(rút gọn 1979 ở cả tử và mẫu)

=1000

Câu hỏi là gì?

\(A=\frac{2007\cdot\left(2008-1008\right)}{\left(2007-1007\right)+\left(2008-1008\right)}=\frac{2007\cdot1000}{1000+1000}=\frac{2007}{2}\)

\(B=\frac{1978\cdot1979+\left(1979+1\right)\cdot21+\left(1979-21\right)}{1979\cdot\left(1980-1978\right)}=\frac{1979\cdot\left(1978+21\right)}{1979\cdot2}=\frac{1999}{2}\)

Đáp án là \(\frac{64}{403}\)bạn nhé !

A= 5 x (4/31.7.5 + 6/7.5.41 + 9/41.10.5 + 7/ 10.5.57 + 1958/57.403.5)

   = 5 x (4/31.35 + 6/35.41 + 9/41.50 + 7/50.57 + 1958/57.2015)

   =5 x (1/31 - 1/35 + 1/35 - 1/41 + 1/41 - 1/50 + 1/50 - 1/57 + 1/57 - 1/2015)

   = 5 x (1/31 - 1/2015)

   = 5 x (65/2015 - 1/2015)

   = 5 x 64/2015

   = 320/2015 = 64/403

=1001 nkaq bn 

mk nka

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

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

Nhớ tick và theo dõi mik nhá!

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