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Bài 1:
b) \(71+65.4=\frac{x+140}{x}+260\)
\(\Rightarrow331=\frac{x+140}{x}+260\)
\(\Rightarrow\frac{x+140}{x}=71\)
\(\Rightarrow x+140=71x\)
\(\Rightarrow71x-x=140\)
\(\Rightarrow70x=140\)
\(\Rightarrow x=2\)
Vậy ...
c) \(7:\left(\frac{3,8.x}{19}+3\right)=1,75\)
\(\frac{3,8.x}{19}+3=4\)
\(\frac{3,8.x}{19}=1\)
\(3,8.x=19\)
\(x=5\)
vaayj ...
\(7:\left(\dfrac{3,8\times y-57}{19}+3\right)=1,75\)
\(\Rightarrow\left(\dfrac{3,8\times y-57}{19}+3\right)=7:1,75\)
\(\Rightarrow\dfrac{3,8\times y-57}{19}+3=4\)
\(\Rightarrow\dfrac{3,8\times y-57}{19}=4-3\)
\(\Rightarrow\dfrac{3,8\times y-57}{19}=1\)
\(\Rightarrow3,8\times y-57=1\times19\)
\(\Rightarrow3,8\times y-57=19\)
\(\Rightarrow3,8\times y=19+57\)
\(\Rightarrow3,8\times y=76\)
\(\Rightarrow y=76:3,8\)
\(\Rightarrow y=20\)
\(7:\frac{5.8.x-57}{19+3}=7.\frac{22}{40x-57}=1775\)
<=> \(\frac{154}{40x-57}=1775=>x=\frac{154+1775.57}{40}\)
\(\frac{x}{19}<\frac{7}{57}\)
Ta có \(\frac{x}{19}=\)\(\frac{x.3}{19.3}=\frac{x.3}{57}\)
=> x = 0;1;2