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a) 213213/104104 = 213/104 ; 137137/70070 = 137/70
2 = 208/104 < 213/104 ; 2 = 140/70 > 137/70
=> 213/104 > 137/70 => 213213/104104 > 137137/70070
b) 1 - 21/52 = 31/52 = 310/520
1 - 213/523 = 310/523
Mà 310/520 > 310/523 => 21/52 < 213/523
a, >
b, <
~~ tk mk nha ~~
Ai tk mk mk tk lại ~!~ ^^
kb nha ~ n_n
a)\(=\frac{-3}{7}+\frac{15}{26}-\frac{2}{13}+\frac{3}{7}\)
\(=\left(\frac{-3}{7}+\frac{3}{7}\right)-\left(\frac{15}{26}+\frac{2}{13}\right)\)
\(=0-\frac{19}{26}\)
\(=-\frac{19}{26}\)
c)\(=\frac{-11}{23}.\left(\frac{6}{7}+\frac{8}{7}\right)-\frac{1}{23}\)
\(=\frac{-11}{23}.2-\frac{1}{23}\)
\(=\frac{-22}{23}-\frac{1}{23}\)
\(=-1\)
Bài 1:
a) Ta có: \(\frac{3}{5}+\frac{4}{15}\)
\(=\frac{9}{15}+\frac{4}{15}\)
\(=\frac{13}{15}\)
b) Ta có: \(\frac{-3}{5}+\frac{5}{7}\)
\(=\frac{-21}{35}+\frac{25}{35}=\frac{4}{35}\)
c) Ta có: \(\frac{5}{6}:\frac{-7}{12}\)
\(=\frac{5}{6}\cdot\frac{-12}{7}=\frac{-60}{42}=\frac{-10}{7}\)
d) Ta có: \(\frac{-21}{24}:\frac{-14}{8}\)
\(=\frac{-7}{8}:\frac{-7}{4}\)
\(=\frac{-7}{8}\cdot\frac{4}{-7}=\frac{4}{8}=\frac{1}{2}\)
e) Ta có: \(\frac{-3}{5}\cdot\frac{5}{7}+\frac{-3}{5}\cdot\frac{3}{7}+\frac{-3}{5}\cdot\frac{6}{7}\)
\(=\frac{-3}{5}\left(\frac{5}{7}+\frac{3}{7}+\frac{6}{7}\right)\)
\(=-\frac{3}{5}\cdot2=\frac{-6}{5}\)
f) Ta có: \(\frac{1}{3}\cdot\frac{4}{5}+\frac{1}{3}\cdot\frac{6}{5}-\frac{4}{3}\)
\(=\frac{1}{3}\cdot\frac{4}{5}+\frac{1}{3}\cdot\frac{6}{5}-\frac{1}{3}\cdot4\)
\(=\frac{1}{3}\left(\frac{4}{5}+\frac{6}{5}-4\right)\)
\(=\frac{1}{3}\cdot\left(-2\right)=\frac{-2}{3}\)
g) Ta có: \(\frac{4}{19}\cdot\frac{-3}{7}+\frac{-3}{7}\cdot\frac{5}{19}+\frac{5}{7}\)
\(=\frac{4}{19}\cdot\frac{-3}{7}+\frac{5}{19}\cdot\frac{-3}{7}+\frac{-3}{7}\cdot\frac{5}{-3}\)
\(=-\frac{3}{7}\left(\frac{4}{19}+\frac{5}{19}+\frac{-5}{3}\right)\)
\(=\frac{-3}{7}\cdot\left(\frac{27}{57}+\frac{-95}{57}\right)\)
\(=\frac{-3}{7}\cdot\frac{-68}{57}=\frac{68}{133}\)
h) Ta có: \(\frac{5}{9}\cdot\frac{7}{13}+\frac{5}{9}\cdot\frac{9}{13}-\frac{5}{9}\cdot\frac{3}{13}\)
\(=\frac{5}{9}\left(\frac{7}{13}+\frac{9}{13}-\frac{5}{13}\right)\)
\(=\frac{5}{9}\)
\(\frac{1}{1}\)_\(\frac{-1}{1}\)_\(\frac{1}{1}\)_..._\(\frac{1}{1}\)
bài 2:
a)\(A=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{999}-\frac{1}{1000}\)
\(=1-\frac{1}{1000}\)
\(=\frac{999}{1000}\)
mk ko biết bn có sai đề ko nhưng mk chỉ lm theo ý mk hiểu thôi! sai thì thôi nha!
bn làm như vầy nè
a=1/51+1/52+...+1/100
A=1/3.1/7 + 1/2.1/26+....1/2.1/50
A=1/3-1/7+1/2-1/26+...1/2-1/50
A=1/3-1/50
A=47/50
như vầy đó bn tin mik đi
\(\frac{213213213:1001001-213213:1001+213213213213:1001001001}{142142142:1001001-142142:1001+142142142142:1001001001}\)
= \(\frac{213-213+213}{142-142+142}\)
=\(\frac{213}{142}\)
\(\frac{213213213-213213+213213213213}{142142142-142142+142142142142}\)
\(=\frac{213.\left(1001001-1001+1001001001\right)}{142.\left(1001001-1001+1001001001\right)}\)
\(=\frac{213}{142}\)
\(=\frac{3}{2}\)
~ Ủng hộ nhé