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b)\(\dfrac{1}{7}B=\dfrac{1}{10.18}+\dfrac{1}{18.26}+\dfrac{1}{26.34}+...+\dfrac{1}{802.810}\)
\(\dfrac{1}{7}B=\dfrac{1}{8}\left(\dfrac{8}{10.18}+\dfrac{8}{18.26}+\dfrac{8}{26.34}+...+\dfrac{8}{802.810}\right)\)
\(\dfrac{1}{7}B=\dfrac{1}{8}\left(\dfrac{1}{10}-\dfrac{1}{18}+\dfrac{1}{18}-\dfrac{1}{26}+\dfrac{1}{26}-\dfrac{1}{34}+...+\dfrac{1}{802}-\dfrac{1}{810}\right)\)
\(\dfrac{1}{7}B=\dfrac{1}{8}\left(\dfrac{1}{10}-\dfrac{1}{810}\right)\)
\(\dfrac{1}{7}B=\dfrac{1}{8}.\dfrac{8}{81}\)
\(\dfrac{1}{7}B=\dfrac{1.8}{8.81}\)
\(\dfrac{1}{7}B=\dfrac{1}{81}\)
\(B=\dfrac{1}{81}:\dfrac{1}{7}\)
\(B=\dfrac{7}{81}\)
\(\dfrac{3x}{2.5}+\dfrac{3x}{5.8}+\dfrac{3x}{8.11}+\dfrac{3x}{11.14}=\dfrac{1}{21}\)
\(\Rightarrow x\left(\dfrac{3}{2.5}+\dfrac{3}{5.8}+\dfrac{3}{8.11}+\dfrac{3}{11.14}\right)=\dfrac{1}{21}\)
\(\Rightarrow x\left(\dfrac{1}{2}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{8}+\dfrac{1}{8}-\dfrac{1}{11}+\dfrac{1}{11}-\dfrac{1}{14}\right)=\dfrac{1}{21}\)
\(\Rightarrow x\left(\dfrac{1}{2}-\dfrac{1}{14}\right)=\dfrac{1}{21}\)
\(\Rightarrow x.\dfrac{3}{7}=\dfrac{1}{21}\)
\(\Rightarrow x=\dfrac{1}{21}.\dfrac{7}{3}\)
\(\Rightarrow x=\dfrac{1}{9}\)
Vậy \(x=\dfrac{1}{9}\)
3/ Chu vi hình chữ nhật:
\(\left(\dfrac{1}{4}+\dfrac{3}{10}\right)\cdot2=\dfrac{11}{10}\) (chưa biết đơn vị)
Diện tích hình chữ nhật:
\(\dfrac{1}{4}\cdot\dfrac{3}{10}=\dfrac{11}{20}\) (chưa biết đơn vị)
a) Ta có :
\(x:4\dfrac{1}{3}=-2,5\)
\(x=-2,5\times4\dfrac{1}{3}\)
\(x=-\dfrac{65}{6}\)
b) Ta có :
\(x:\dfrac{-3}{5}=\dfrac{-10}{21}\)
\(x=\dfrac{-10}{21}\times\dfrac{-3}{5}\)
\(x=\dfrac{2}{7}\)
c)\(\dfrac{2}{3}x-\dfrac{1}{2}=\dfrac{1}{10}\)
\(\dfrac{2}{3}x=\dfrac{1}{10}+\dfrac{1}{2}\)
\(\dfrac{2}{3}x=\dfrac{3}{5}\)
\(x=\dfrac{3}{5}:\dfrac{2}{3}\)
\(x=\dfrac{3}{5}\)
d) \(\dfrac{1}{2}x+\dfrac{1}{2}=\dfrac{5}{2}\)
\(\dfrac{1}{2}x=2\)
\(x=2:\dfrac{1}{2}\)
\(x=4\)
~ Chúc bn học tốt ~
a, \(x:4\dfrac{1}{3}=-2,5.\)
\(x:\dfrac{13}{3}=\dfrac{-5}{2}.\)
\(x=\dfrac{-5}{2}.\dfrac{13}{3}.\)
\(x=\dfrac{-65}{6}.\)
b, \(x:\dfrac{-3}{5}=\dfrac{-10}{21}.\)
\(x=\dfrac{-10}{21}.\dfrac{-3}{5}.\)
\(x=\dfrac{30}{105}=\dfrac{2}{7}.\)
c, \(\dfrac{2}{3}x-\dfrac{1}{2}=\dfrac{1}{10}.\)
\(\dfrac{2}{3}x=\dfrac{1}{10}+\dfrac{1}{2}.\)
\(\dfrac{2}{3}x=\dfrac{1}{10}+\dfrac{5}{10}.\)
\(\dfrac{2}{3}x=\dfrac{3}{5}.\)
\(x=\dfrac{3}{5}:\dfrac{2}{3}.\)
\(x=\dfrac{3}{5}.\dfrac{3}{2}.\)
\(x=\dfrac{9}{10}.\)
d, \(\dfrac{1}{2}x+\dfrac{1}{2}=\dfrac{5}{2}.\)
\(\dfrac{1}{2}x=\dfrac{5}{2}-\dfrac{1}{2}.\)
\(\dfrac{1}{2}x=2.\)
\(x=2:\dfrac{1}{2}.\)
\(x=2.2.\)
\(x=4.\)
~ Chúc bn học tốt!!! ~
Bài mik đúng thì nhớ tick mik nha!!!
1,=0 . [2017/2018+2018/2019]
=>0
2,TH1 x-3=0=>x=3
TH2 y-4=0=>y=4
3, -2/4 = -x/10 = 16/y
=>-1/2 = -x/10 = 16/y
=>-1/2 = -x/10 => -5/10 = -x/10 => x=5
-1/2 = 16/y => 16/-32 = 16/y => y = -32
a, \(\dfrac{x+2}{2}=\dfrac{6}{12}\Rightarrow6x+12=6\Leftrightarrow x=-1\)
b, đk : x khác 1
\(\dfrac{8}{x-1}=-\dfrac{16}{22}=-\dfrac{8}{11}\Rightarrow x-1=-11\Leftrightarrow x=-10\)(tm)
thank
