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

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

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

   1978x1979 + 1980x21+ 1958 / 1980x1979 - 1978x1979

= 1978x1979+ (1978+2)x21 + 1958 / (1980 - 1978) x 1979

= 1978x1979+ 1978x21+2x21+1958 / 2x1979

= 1978x1979 + 1978x21+ 2000 / 2x1979

= 1978 x (1979 + 21) + 2000 / 1979 x 2

= 1978x 2000+2000 / 1979 x2

= 1978 x 2000+2000 / (1978 +1) x2

= 1978 x 2000+2000/ 1978x2 + 2

= 2000+2000 / 2+2

= 4000 / 4

= 1000

L - i - k - e nha

thank you

cam on nhe 

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

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

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

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

= \(\frac{1978+21+1}{2}\)

= \(\frac{2000}{2}\)= 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?

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

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

\(1978\cdot1979+1980\cdot21+\frac{1958}{1980}\cdot1979-1978\cdot1979\)

\(=1980\cdot21+\frac{89}{90}\cdot1979\)

\(=41580+\frac{176131}{90}\)

\(=\frac{3918331}{90}\)

Đề có sai ko mà sao thấy số lớn wá.

\(\frac{1978\cdot1979+1980\cdot21+1958}{1980\cdot1979-1978\cdot1979}=\frac{1978\cdot1979+\left(1979+1\right)\cdot21+1958}{1979\cdot\left(1980-1978\right)}\)

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

1000 đó bạn ơi chuẩn 10000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000%luôn đó bạn

1000 đó bạn 

đáp án là 1000.chính xác nhất!OK

nguyễn trung hiếu bấm máy chứ gì 

Đáp án là 1975.210114

xin lỗi do mình tính nhanh thôi

(1978.1979+1980.21+1958)/(1980.1979+1978... 
= (1978.1979+1979.21 + 21 + 1958 )/(1980.1979+1978.1979) 
= (1978.1979+1979.21 + 1979 )/[(1980+1978).1979)] 
= [(1978 + 21+1).1979]/[(1980+1978).1979)] = (2000.1979)/(2.1979.1979) 
= 2000/(2.1979)=1000/1979