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MN
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DT
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LV
30 tháng 6 2018 lúc 9:20

\(B=\dfrac{120-\left(-0,5\right)\cdot\left(-40\right)\cdot\left(-5\right)\cdot\left(-0,2\right)\cdot20\cdot0\cdot25}{5+10+15+...+2015}\\ =\dfrac{120-0}{5+10+15+...+2015}\\ =\dfrac{120}{5+10+15+...+2015}\\ ĐặtA=5+10+15+2015\\ A=\left(2015+5\right)\cdot\left[\left(2015-5\right):5+1\right]:2\\ A=407030\\ VậyB=\dfrac{120}{407030}=\dfrac{6}{203515}\)

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NB
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H24
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NT
27 tháng 7 2023 lúc 20:04

=(2căn 5-căn 2)(2căn 5+căn 2)

=20-2=18

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NL
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TD
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LT
25 tháng 9 2015 lúc 16:59

cậu đăng nhiều quá tớ ngại

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TS
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ND
29 tháng 10 2017 lúc 13:56

đây là toán lớp 5

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H24
29 tháng 10 2017 lúc 14:08

\(\left(\frac{9}{25}-2,18\right):\left(3\frac{4}{5}+0,2\right)\)

\(=\left(\frac{9}{25}-\frac{109}{50}\right):\left(\frac{19}{5}+\frac{1}{5}\right)\)

\(=\frac{-91}{50}:4=\frac{-91}{200}\)

\(\frac{5}{18}-1,456:\frac{7}{15}+4,5.\frac{4}{5}\)

\(=\frac{5}{18}-\frac{182}{125}.\frac{15}{7}+\frac{18}{5}\)

\(=\frac{5}{18}-\frac{78}{25}+\frac{18}{5}\)

\(=\frac{341}{450}\)

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DM
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MV
3 tháng 8 2017 lúc 19:39

a,

\(\dfrac{4^2\cdot4^3}{2^{10}}=\dfrac{4^5}{2^{10}}=\dfrac{\left(2^2\right)^5}{2^{10}}=\dfrac{2^{10}}{2^{10}}=1\)

b,

\(\dfrac{\left(0,6\right)^5}{\left(0,2\right)^6}=\dfrac{\left(0,2\cdot3\right)^5}{\left(0,2\right)^5\cdot0,2}=\dfrac{\left(0,2\right)^5\cdot3^5}{\left(0,2\right)^5\cdot0,2}=\dfrac{243}{0,2}=\dfrac{243}{\dfrac{1}{5}}=243\cdot5=1215\)

c,

\(\dfrac{2^7\cdot9^3}{6^5\cdot8^2}=\dfrac{2^7\cdot\left(3^2\right)^3}{\left(2\cdot3\right)^5\cdot\left(2^3\right)^2}=\dfrac{2^6\cdot2\cdot3^6}{2^5\cdot3^5\cdot2^6}=\dfrac{3}{2^4}=\dfrac{3}{16}\)

d,

\(\dfrac{6^3+3\cdot6^2+3^3}{-13}=\dfrac{\left(2\cdot3\right)^3+3\cdot\left(2\cdot3\right)^2+3^3}{-13}=\dfrac{2^3\cdot3^3+3\cdot2^2\cdot3^2+3^3}{-13}=\dfrac{2^3\cdot3^3+2^2\cdot3^3+3^3}{-13}\dfrac{3^3\left(2^3+2^2+1\right)}{-13}=\dfrac{3^3\cdot13}{-13}=-3^3=-27\)

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CT
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H24
27 tháng 6 2017 lúc 14:44

a) \(\dfrac{3}{4}-\dfrac{1}{2}x=-\dfrac{1}{4}\)

\(\Leftrightarrow3-2x=-1\)

\(\Leftrightarrow-2x=-1-3\)

\(\Leftrightarrow-2x=-4\)

\(\Leftrightarrow x=2\)

Vậy \(x=2\)

b) \(1\dfrac{2}{3}x+0,2=x-\dfrac{7}{8}\)

\(\Leftrightarrow\dfrac{5}{3}x+\dfrac{1}{5}=x-\dfrac{7}{8}\)

\(\Leftrightarrow200x+24=120x-105\)

\(\Leftrightarrow80x=-129\)

\(\Leftrightarrow x=-\dfrac{129}{80}\)

Vậy \(x=-\dfrac{129}{80}\)

c) \(\dfrac{3}{4}-\left|x+0,5\right|=\dfrac{1}{5}\)

\(\Leftrightarrow-\left|x+0,5\right|=\dfrac{1}{5}-\dfrac{3}{4}\)

\(\Leftrightarrow-\left|x+0,5\right|=-\dfrac{11}{20}\)

\(\Leftrightarrow\left|x+0,5\right|=\dfrac{11}{20}\)

\(\Leftrightarrow\left[{}\begin{matrix}x+0,5=\dfrac{11}{20}\\x+0,5=-\dfrac{11}{20}\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{1}{20}\\x=-\dfrac{21}{20}\end{matrix}\right.\)

Vậy \(x_1=-\dfrac{21}{20};x_2=\dfrac{1}{20}\)

d) \(\left(x+0,2\right)^2+0,75=1\)

\(\Leftrightarrow\left(x+\dfrac{1}{5}\right)^2+\dfrac{3}{4}=1\)

\(\Leftrightarrow\left(x+\dfrac{1}{5}\right)^2=1-\dfrac{3}{4}\)

\(\Leftrightarrow\left(x+\dfrac{1}{5}\right)^2=\dfrac{1}{4}\)

\(\Leftrightarrow x+\dfrac{1}{5}=\pm\dfrac{1}{2}\)

\(\Leftrightarrow\left[{}\begin{matrix}x+\dfrac{1}{5}=\dfrac{1}{2}\\x+\dfrac{1}{5}=-\dfrac{1}{2}\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{3}{10}\\x=-\dfrac{7}{10}\end{matrix}\right.\)

Vậy \(x_1=-\dfrac{7}{10};x_2=\dfrac{3}{10}\)

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SP
27 tháng 6 2017 lúc 15:33

a, \(\dfrac{3}{4}-\dfrac{1}{2}x=-\dfrac{1}{4}\)

=>\(-\dfrac{1}{2}x=-\dfrac{1}{4}-\dfrac{3}{4}\)

=>\(-\dfrac{1}{2}x=-1\)

=>\(x=-1:(-\dfrac{1}{2})\)

=>\(x=2\)

vậy ...........

b,\(1\dfrac{2}{3}x+0,2=x-\dfrac{7}{8}\)

=>\(\dfrac{5}{3}x+0,2=x-\dfrac{7}{8}\)

=>\(\dfrac{5}{3}x-x=-\dfrac{7}{8}-0,2\)

=>\(\dfrac{2}{3}x=-\dfrac{43}{40}\)

=>\(x=-\dfrac{43}{40}:\dfrac{2}{3}\)

=>\(x=-\dfrac{192}{80}\)

vậy...................

c,\(\dfrac{3}{4}-\left|x+0,5\right|=\dfrac{1}{5}\)

=>\(-\left|x+0,5\right|=\dfrac{1}{5}-\dfrac{3}{4}\)

=>\(-\left|x+0,5\right|=-\dfrac{11}{20}\)

=>\(\left|x+0,5\right|=\dfrac{11}{20}\)

=>\(\left[{}\begin{matrix}x+0.5=\dfrac{11}{20}\\x+0,5=-\dfrac{11}{20}\end{matrix}\right.\)

=>\(\left[{}\begin{matrix}x=\dfrac{1}{20}\\x=-\dfrac{21}{20}\end{matrix}\right.\)

vậy ....... hoặc.....

d,\((x+0,2)^2+0,75=1\)

=>\(\left(x+0,2\right)^2=1-0,75\)

=>\(\left(x+0,2\right)^2=0,25\)

=>\(\left[{}\begin{matrix}x+0,2=0,5\\x+0,2=-0,5\end{matrix}\right.\)

=>\(\left[{}\begin{matrix}x=0,3\\x=-0,7\end{matrix}\right.\)

vậy..........................

HỌC TỐT NHA !!!!!

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