64 x 867 + 867 x 36 - 30 x 867

= 867 x ( 64 + 36 - 30 )

= 867 x 70

= 60 690

\(64\times867+867\times36-30\times867\)

\(=867\times\left(64+24-30\right)\)

\(=867\times70\)

\(=60690\)

64 x 867 + 867 x 36 - 30 x 867 

= 867 (64 + 36 - 30)

= 867 * 70 

= 60690

=867 x ( 64 + 36 - 30)

=867x 70

=60690

ghi sai đề ak, có 2 dấu trừ ở phép số 2

bn phai kb mik mi tra loi

a,2009x867+2009x133=2009x(867+133)=2009x1000=2009000

b,có vẻ sai đề.

 8 x 427 x 3 + 6 x 573 x 4

= 8 x 3 x 427 + 6 x 4 x 573

= 24 x 427 + 24 x 573

= 24 x (427 + 573)

= 24 x 1000

= 24000

 2008 x 867 + 2009 x 133

= 2008 x 867 + 2008 x 133 + 133

= 2008 x (867 + 133) + 133

= 2008 x 1000 + 133

= 2008133

tick cho mink nhé

\(\Leftrightarrow\dfrac{2032-x}{25}-1+\dfrac{2053-x}{23}-2+\dfrac{2070-x}{21}-3+\dfrac{2083-x}{19}-4=0\)

=>2007-x=0

hay x=2007

\(\dfrac{2032-x}{25}+\dfrac{2053-x}{23}+\dfrac{2070-x}{21}+\dfrac{2083-x}{19}=10\)

\(\Leftrightarrow\left(\dfrac{2032-x}{25}-1\right)+\left(\dfrac{2053-x}{23}-2\right)+\left(\dfrac{2070-x}{21}-3\right)+\left(\dfrac{2083-x}{19}-4\right)=0\)

\(\Leftrightarrow\dfrac{2032-x-25}{25}+\dfrac{2053-x-46}{23}+\dfrac{2070-x-63}{21}+\dfrac{2083-x-76}{19}=0\)

\(\Leftrightarrow\dfrac{2007-x}{25}+\dfrac{2007-x}{23}+\dfrac{2007-x}{21}+\dfrac{2007-x}{19}=0\)

\(\Leftrightarrow\left(2007-x\right)\left(\dfrac{1}{25}+\dfrac{1}{23}+\dfrac{1}{21}+\dfrac{1}{19}\right)=0\)

\(\Leftrightarrow2007-x=0\left(vì.\dfrac{1}{25}+\dfrac{1}{23}+\dfrac{1}{21}+\dfrac{1}{19}\ne0\right)\)

\(\Leftrightarrow x=2007\)

tui chỉ làm phần b thôi há !

B=\(\frac{3}{4}\)+\(\frac{27}{28}\)+\(\frac{69}{70}\)+...+\(\frac{867}{868}\)=\(\frac{4-1}{4}\)+\(\frac{28-1}{28}\)+\(\frac{70-1}{70}\)+...+\(\frac{868-1}{868}\)

= 1+1+..+1 -(\(\frac{1}{4}\)+\(\frac{1}{28}\)+\(\frac{1}{70}\)+...+\(\frac{1}{868}\)) = 10 - \(\frac{1}{3}\)(\(\frac{3}{1.4}\)+\(\frac{3}{4.7}\)+\(\frac{3}{7.10}\)+...+\(\frac{3}{28.31}\))

=10-\(\frac{1}{3}\)(1-\(\frac{1}{4}\)+\(\frac{1}{4}\)-\(\frac{1}{7}\)+\(\frac{1}{7}\)-\(\frac{1}{10}\)+...+\(\frac{1}{28}\)-\(\frac{1}{30}\))=10-\(\frac{1}{3}\)(1-\(\frac{1}{30}\))=10-\(\frac{1}{3}\).\(\frac{29}{30}\)=10-\(\frac{29}{30}\)=\(\frac{271}{30}\)

\(1994x867+1995x133\)

\(=1994x867+\left(1994+1\right)x133\)

\(=1994x867+1994x133+133\)

\(=1994x\left(867+133\right)+133\)

\(=1994x1000+133\)

\(=1994000+133\)

\(=1994333\)

Chúc bạn học tốt !!!! 

Đánh nhầm : \(1994133\)

1994 x 867 + 1995 x 133

= 1994 x 867 + ( 1994 + 1 ) x 133

= 1994 x 867 + 1994 x 133 + 133

= 1994 x ( 867+133) + 133

= 1994 x 1000 + 133

= 1994000+ 133

= 1994133
 

\(1994\times867+1995\times133\)

\(=1994\times867+1994\times133+133\)

\(=1994\times\left(867+133\right)+133\)

\(=1994\times1000+133\)

\(=1994000+133\)

\(=1994133\)