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\(y\times\dfrac{1}{2}+y\times\dfrac{1}{6}+y\times\dfrac{1}{12}+y\times\dfrac{1}{20}=\dfrac{8}{5}\)
\(y\times\left(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}\right)=\dfrac{8}{5}\)
\(y\times\dfrac{4}{5}=\dfrac{8}{5}\)
\(\dfrac{8}{5}:\dfrac{4}{5}\)
\(y=\dfrac{8}{4}=2\)
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`1716:y=12xx13`
`1716:y=156`
`y=1716:156`
`y=11`
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`y xx 2/3+y xx 1/6=10/3`
`y xx(2/3+1/6)=10/3`
`y xx(4/6+1/6)=10/3`
`y xx5/6=10/3`
`y=10/3:5/6`
`y=10/3xx6/5=4`
1716 : y = 12 \(\times\) 13
1716 : y = 156
y = 1716 : 156
y = 11
\(y\times\dfrac{2}{3}+y\times\dfrac{1}{6}=\dfrac{10}{3}\)
\(y\times\left(\dfrac{2}{3}+\dfrac{1}{6}\right)=\dfrac{10}{3}\)
\(y\times\dfrac{5}{6}=\dfrac{10}{3}\)
\(y=\dfrac{10}{3}:\dfrac{5}{6}\)
\(y=4\)
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\(\dfrac{4}{x}=\dfrac{12}{15}=\dfrac{y}{45}\)
Ta có:
\(12:4=3\)
\(\Rightarrow\dfrac{4}{x}=\dfrac{4\times3}{x\times3}=\dfrac{12}{15}\)
Mà \(15:3=5\)
\(\Rightarrow x=5\)
Lại có:
\(45:15=3\)
\(\Rightarrow\dfrac{12}{15}=\dfrac{12\times3}{15\times3}=\dfrac{y}{45}\)
Mà \(12\times y=36\)
\(\Rightarrow y=36\)
Vậy \(x=5;y=36\).
\(\dfrac{3}{x}=\dfrac{1}{y}=\dfrac{6}{24}\)
Ta có:
\(\dfrac{3}{x}=\dfrac{6}{24}\)
\(6\times x=3\times24\)
\(6\times x=72\)
\(x=72:6\)
\(x=12\)
\(\Rightarrow x=12\)
Lại có:
\(\dfrac{3}{12}=\dfrac{1}{y}\)
\(3\times y=1\times12\)
\(3\times y=12\)
\(y=12:3\)
\(y=4\)
\(\Rightarrow y=4\)
Vậy \(x=12;y=4\).
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=>( y - 1/2 )+( y - 1/6 )+...+( y- 1/90 ) = 1
=>y + y+.. + y - 1/2 - 1/6-...- 1/90 = 1
=>y + y+..+ y - 1/(1x2) - 1/(2x3) - 1/(3x4)-...- 1/(9x10) = 1
=> 9y -( 2-1)/(1x2) - (3-2)/(2x3)-...- (10-9)/(9x10) = 1
=>9y- 2/(1x2) + 1(1x2) - 3/(2x3) + 2/(2x3)-...- 10/(9x10) + 9(9x10) = 1
=> 9y- 1 + 1/2 - 1/2 + 1/3-...- 1/9 + 1/10 = 1
=>9y- 1 + 1/10 = 1
=> 9y- 9/10 =1
=>y=19/90
Vậy y=19/90
y=19/10