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\(3\times x=\dfrac{1}{3}\)
\(x=\dfrac{1}{3}:3\)
\(x=\dfrac{1}{9}\)
\(3\cdot x=\dfrac{1}{3}\\ x=\dfrac{1}{3}:3\\ x=\dfrac{1}{9}\)
`x xx 6/7=5/14`
`=>x=5/14:6/7`
`=>x=5/14xx7/6`
`=>x=35/84`
`=>x=5/12`
Vậy `x=5/12`
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`x:2/3=4/9`
`=>x=4/9xx2/3`
`=>x=8/27`
Vậy `x=8/27`
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`x-1/4=3/2`
`=>x=3/2+1/4`
`=>x=6/4+1/4`
`=>x=7/4`
Vậy `x=7/4`
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`x+4/5=8/9`
`=>x=8/9-4/5`
`=>x=40/45-36/45`
`=>x=4/45`
Vậy `x=4/45`
\(x\cdot\dfrac{6}{7}=\dfrac{5}{14}\)
\(x\) \(=\dfrac{5}{14}:\dfrac{6}{7}\)
\(x\) \(=\dfrac{5}{12}\)
\(x:\dfrac{2}{3}=\dfrac{4}{9}\)
\(x\) \(=\dfrac{4}{9}\cdot\dfrac{2}{3}\)
\(x\) \(=\dfrac{8}{27}\)
\(x-\dfrac{1}{4}=\dfrac{3}{2}\)
\(x\) \(=\dfrac{3}{2}+\dfrac{1}{4}\)
\(x\) \(=\dfrac{7}{4}\)
\(x+\dfrac{4}{5}=\dfrac{8}{9}\)
\(x\) \(=\dfrac{8}{9}-\dfrac{4}{5}\)
\(x\) \(=\dfrac{4}{45}\)
a. \(=\left(\dfrac{12}{15}+\dfrac{3}{15}\right)+\left(\dfrac{4}{3}+\dfrac{5}{3}\right)+\left(\dfrac{1}{4}+\dfrac{3}{4}\right)\\ =1+2+1=4\)
b. \(x\times\dfrac{3}{4}=\dfrac{1\times3\times6\times5}{6\times5\times5\times3}\\ x\times\dfrac{3}{4}=\dfrac{1}{5}\\ x=\dfrac{1}{5}:\dfrac{3}{4}\\ x=\dfrac{4}{15}\)
Ta có : \(\frac{1}{3.7}+\frac{1}{7.11}+...+\frac{1}{x.\left(x+4\right)}=\frac{5}{63}\)
=> \(\frac{1}{4}.\left(\frac{4}{3.7}+\frac{4}{7.11}+...+\frac{4}{x\left(x+4\right)}\right)=\frac{5}{63}\)
=> \(\frac{1}{3}-\frac{1}{7}+\frac{1}{7}-\frac{1}{11}+...+\frac{1}{x}-\frac{1}{x+1}=\frac{20}{63}\)
=> \(\frac{1}{3}-\frac{1}{x+1}=\frac{20}{63}\)
=> \(\frac{1}{x+1}=\frac{1}{63}\)
=> x + 1 = 63
=> x = 62
Vậy x = 62
Sửa lại bài làm của XYZ một chút:
=> \(\frac{1}{3}-\frac{1}{7}+\frac{1}{7}-\frac{1}{11}+..+\)\(\frac{1}{x}-\frac{1}{x+4}\)
=> \(\frac{1}{3}-\frac{1}{x+4}\)= \(\frac{5}{63}\div\frac{1}{4}=\frac{20}{63}\)f
đố cấn thận vào