10 bn nhanh nhất nha
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câu
e) 99 - 97 + 95 - 93 + 91 - 89 + .... + 7 - 5 + 3 - 1
= 2 + 2 + 2 + ..... + 2 ( có 49 số 2 )
= 2 x 20
= 40
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a) 35.93.272
=35.(32)3.(33)2
=35.36.36
=3(5+6+6)
=317
b) 42.23.82
=(22)2.23.(23)2
=24.23.26
=2(4+6+3)
=213
c)625.125
=54.53
=5(4+3)
=57
d)1000.100.104
=103.102.104
=10(3+4+2)
=109
e)84.163.32
=(23)4.(24)3.25
=212.212.25
=2(12+12+5)
=229
mik làm giúp bạn rồi nhé!!!
![](https://rs.olm.vn/images/avt/0.png?1311)
mình làm cho 2 bài khó thôi
e) 22 + 23 + 24 + .... + 27 + 28
= ( 28 + 22 ) x 7 : 2
= 175
f) 12 + 14 + 16 + 18 + 30
= ( 18 + 12 ) x 4 : 2 + 30
= 60 + 30
= 90
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c) \(\left(20+9\frac{1}{4}\right):2\frac{1}{4}=\)
\(=\left(20+9,25\right):2,25\)
\(=29,25:2,25\)
\(=13\)
HOk tốt!!!!!!!!!!!!
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S=1−2+2^2−2^3+....+2^2002
2S=2−2^2+2^3−2^4+...+2^2003
2S+S=(2−2^2+2^3−2^4+...+2^2003)+(1−2+2^2−2^3+....+2^2002)
3S=2^2003+1
3S−2^2003
=2^2003+1−1
=2^2003
![](https://rs.olm.vn/images/avt/0.png?1311)
Bài 5 : \(S=-\left(a-b-c\right)+\left(-c+b-a\right)-\left(a+b\right)\)
\(A=-a+b+c-c+b-a-a-b=-3a+b\)
\(A=-2a-\left(a-b\right)=-2a-1\)
\(S=1-2+2^2-2^3+...+2^{2002}\)
\(2S=2-2^2+2^3-...-2^{2002}+2^{2003}\)
\(2S-S=\left(2-2^2+...+2^{2003}\right)-\left(1-2+...+2^{2002}\right)\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(a,\frac{3}{4}.\frac{16}{9}-\frac{7}{5}:\frac{-21}{20}\)
\(=\frac{4}{3}-\left(-\frac{4}{3}\right)\)
\(=\frac{8}{3}\)
\(b,2\frac{1}{3}-\frac{1}{3}.\left[\frac{-3}{2}+\left(\frac{2}{3}+0,4.5\right)\right]\)
\(=2\frac{1}{3}-\frac{1}{3}.\left[\frac{-3}{2}+\frac{8}{3}\right]\)
\(=2\frac{1}{3}-\frac{1}{3}.\frac{7}{6}\)
\(=2\frac{1}{3}-\frac{7}{18}\)
\(=\frac{35}{18}\)
\(c,\frac{32}{15}:\left(-1\frac{1}{5}+1\frac{1}{3}\right)\)
\(=\frac{32}{15}:\frac{2}{15}\)
\(=16\)
\(a)\frac{-3}{5}+\frac{7}{21}+\frac{-4}{5}+\frac{7}{5}\)
\(=\frac{7}{21}+\left(\frac{-3}{5}+\frac{-4}{5}+\frac{7}{5}\right)\)
\(=\frac{7}{21}+0=\frac{7}{21}\)
\(b)\frac{-3}{17}+\left(\frac{2}{3}+\frac{3}{17}\right)\)
\(=\frac{-3}{17}+\frac{2}{3}+\frac{3}{17}\)
\(=\left(\frac{-3}{17}+\frac{3}{17}\right)+\frac{2}{3}\)
\(=0+\frac{2}{3}=\frac{2}{3}\)