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a. \(0,5x-\frac{2}{3}x=\frac{7}{12}\)
=>\(\left(0,5-\frac{2}{3}\right).x=\frac{7}{12}\)
=>\(-\frac{1}{6}.x=\frac{7}{12}\)
=>\(x=\frac{7}{12}:-\frac{1}{6}=-\frac{7}{2}\)
_Hok tốt_
b.\(x:4\frac{1}{3}=-2,5\)
=>\(x:\frac{13}{3}=-2,5\)
=>\(x=-2,5.\frac{13}{3}=-\frac{65}{6}\)
_Hok tốt_
0,5x-2/3x=7/12
=>(1/2-2/3).x=7/12
=>-1/6x=7/12
=>x=7/12:1/6
=>x=7/2
b, x:4 1/3=-2,5
=>x:13/3=-2,5
=>x=-5/2x13/3
=>x=-13
c,5,5x=13/15
=>11/2x=13/15
=>x=13/15:11/2
=>x=26/165
d,(3x/7+1):-4=-1/28
=>3x/7+1=-1/28x(-4)
=>3x/7+1=-1/7
=>3x/7=-1/7-1
=>3x/7=-8/7
=>3x=-8/7x7
=>3x=8
=>x=8:3
=>x=8/3
\(0,5x-\frac{2}{3}x=\frac{7}{12}\)
\(\frac{1}{2}x-\frac{2}{3}x=\frac{7}{12}\)
\(\left(\frac{1}{2}-\frac{2}{3}\right)x=\frac{7}{12}\)
\(\frac{-1}{6}x=\frac{7}{12}\)
\(x=-21\)
b,c,d tương tự
\(\frac{1}{1.3}+\frac{1}{3.5}+...+\frac{1}{x.\left(x+2\right)}=\frac{20}{41}\)
\(\Leftrightarrow\frac{1}{2}.\left(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{x}-\frac{1}{x+2}\right)=\frac{20}{41}\)
\(\Leftrightarrow\frac{1}{2}.\left(1-\frac{1}{x+2}\right)=\frac{20}{41}\)
\(\Leftrightarrow1-\frac{1}{x+2}=\frac{20}{41}\div\frac{1}{2}\)
\(\Leftrightarrow1-\frac{1}{x+2}=\frac{40}{41}\)
\(\Leftrightarrow\frac{1}{x+2}=1-\frac{40}{41}\)
\(\Leftrightarrow\frac{1}{x+2}=\frac{1}{41}\)
\(\Leftrightarrow x+2=41\)
\(\Leftrightarrow x=41-2\)
\(\Leftrightarrow x=39\)
\(x-40\%x=3,6\)
\(\Rightarrow100\%x-40\%x=3,6\)
\(\Rightarrow60\%x=3,6\)
\(\Rightarrow\frac{60}{100}x=3,6\)
\(\Rightarrow x=6\)
\(3\frac{2}{7}x-\frac{1}{3}=-2\frac{3}{4}\)
\(\Rightarrow\frac{23}{7}x-\frac{1}{3}=-\frac{11}{4}\)
\(\Rightarrow\frac{23}{7}x=-\frac{33}{12}+\frac{4}{12}\)
\(\Rightarrow\frac{23}{7}x=\frac{29}{12}\)
\(\Rightarrow x=\frac{29}{12}:\frac{23}{7}=\frac{203}{276}\)
\(a,2,5\cdot x=\frac{11}{15}\)
\(\Rightarrow x=\frac{11}{15}:2,5\)
\(\Rightarrow x=\frac{11}{15}:\frac{25}{10}\)
\(\Rightarrow x=\frac{11}{15}\cdot\frac{10}{25}\)
\(\Rightarrow x=\frac{11}{3}\cdot\frac{2}{25}=\frac{22}{75}\)
\(b,x-15\%\cdot x=\frac{1}{3}\)
\(\Rightarrow x-\frac{15}{100}\cdot x=\frac{1}{3}\)
\(\Rightarrow x-\frac{3}{20}\cdot x=\frac{1}{3}\)
\(\Rightarrow\frac{20x}{20}-\frac{3x}{20}=\frac{1}{3}\)
\(\Rightarrow\frac{17x}{20}=\frac{1}{3}\)
\(\Rightarrow17x\cdot3=20\)
\(\Rightarrow17x=\frac{20}{3}\)
\(\Rightarrow x=\frac{20}{3}:17=\frac{20}{3}\cdot\frac{1}{17}=\frac{20}{51}\)
Câu c mk làm sau :v
c,\(\left[\frac{3x}{7}+1\right]:\left[-4\frac{1}{7}\right]=\frac{-3}{28}\)
\(\Rightarrow\left[\frac{3x}{7}+1\right]:\left[-\frac{29}{7}\right]=\frac{-3}{28}\)
\(\Rightarrow\frac{3x}{7}+1=-\frac{3}{28}\cdot-\frac{29}{7}=\frac{87}{196}\)
\(\Rightarrow\frac{3x}{7}=\frac{87}{196}-1\)
Tìm nốt :v
a) \(\frac{5}{6}=\frac{x-1}{x}\)
\(5x=6x-6\)
\(6x-5x=6\)
\(x=6\)
các câu còn lại lm tương tự
hok tốt!!
b) \(\frac{1}{2}=\frac{x+1}{3x}\)
\(\Rightarrow1.3x=2.\left(x+1\right)\)
\(3x=2x+2\)
\(3x-2x=2\)
\(x=2\)
Vậy x=2
các câu khác bạn làm tương tự
\(a\)) \(\frac{x-1}{3}=\frac{4}{2}=2\)
\(x-1=2\times3=6\)
\(x=6+1=7\)
b) \(\left(\frac{3x}{7}+1\right):4=-\frac{1}{28}\)
\(\frac{3x}{7}+1=-\frac{1}{28}\times4=-\frac{1}{7}\)
\(\frac{3x}{7}=-\frac{1}{7}-1=-\frac{8}{7}\)
\(3x=\left(-\frac{8}{7}\right)\times7=-8\)
\(x=-\frac{8}{3}\)
c) \(\frac{2x}{4}=\frac{9}{2}\)
\(2x=\frac{9}{2}\times4\)
\(2x=18\)
\(x=18:2=9\)
a, \(\frac{x-1}{3}=\frac{4}{2}=2\)
\(\Rightarrow x-1=2.3\)
\(x-1=6\)
\(x=6+1\)
\(x=7\)
a) \(\left(\frac{3x}{7}+1\right):\left(-4\right)=\frac{-1}{28}\)
\(\Rightarrow\frac{3}{7}.x+1=\frac{-1}{28}.\left(-4\right)\)
\(\Rightarrow\frac{3}{7}.x=\frac{1}{7}-1\)
\(\Rightarrow\frac{3}{7}.x=\frac{-6}{7}\)
\(\Rightarrow x=\frac{-6}{7}:\frac{3}{7}\)
\(\Rightarrow x=\frac{-6}{7}.\frac{7}{3}\)
\(\Rightarrow x=-2\)
b) x+30%x=-1.3 mình coi 1.3 là 1,3 nhé !
\(\Rightarrow x\left(30\%+1\right)=-1,3\)
\(\Rightarrow x\left(\frac{13}{10}\right)=-\frac{13}{10}\)
\(\Rightarrow x=-\frac{13}{10}:\frac{13}{10}\)
\(\Rightarrow x=-1\)