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a.326.728+327.272
=326.728+326.272+272
=326.(728+272) +272
=326.1000 +272
=326000+272
=326272
B, 1235.6789.(630-315.2)
=1235.6789.(630- 630)
=1235.6789.0
=0
C, 2008.867+2009.133
=2008.867+2008.133 +133
=2008.(867+133)+133
=2008.1000 +133
=2008000+133
=2008133
D, (m:1-m*1) : (m*2008+m+2008)
= (m-m) : (m*2008+m+2008)
= 0 : (m*2008+m+2008)
=0
326 x 728+ 327 × 272 =
237328+88944= 326272
2008 ×867+ 2009× 133 =
1740936+267197=2008133
nhớ k minh nha
326 x 728 + 327 x 272
= 326 x 728 + 326 x 272 + 272
= 326 x ( 728 +272 ) + 272
= 326 x 1000 + 272
= 326000 + 272
= 326272
326 x 728 + 327 x 272
= 326 x 728 + 326 x 272 + 272
= 326 x (728 + 272) + 272
= 326 x 1000 + 272
= 326000 + 272
= 326272
1235 x 6789 x (630 - 315 x 2) : 1996
=1235x6789x(630-630):1996
=1235x6789x0:1996
=0
a, \(\frac{1}{2009}+\frac{2}{2009}+...+\frac{2008}{2009}\\ \frac{\left(1+2008\right)\cdot2008\div2}{2009}=\frac{2017036}{2009}\)
\(2010^2-2009^2+2008^2-...+2^2-1^2\)
\(=-\left(1^2-2^2+3^2-...+2009^2-2010^2\right)\)
\(=-\left[1^2+2^2+...+2009^2+2010^2-\left(2^2+4^2+...+2010^2\right)\right]\)
\(=-\left[\frac{2010.\left(2010-1\right)\left(2.2010-1\right)}{6}-2^2\left(1^2+2^2+...+1005^2\right)\right]\)
\(=-\left[2704847285-2^2.\frac{1005\left(1005-1\right)\left(2.1005-1\right)}{6}\right]\)
\(=-\left(2704847285-1351414120\right)=1353433165\)
