TÌM X
X x 1/2 + X x 1/4 +1/8 x X =21/24
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Bài 1:
a: x/-2=-18/x
=>x2=36
=>x=6 hoặc x=-6
b: x/2+x/5=17/10
=>7/10x=17/10
hay x=17/7
a) \(x\cdot\frac{1}{2}+x\cdot\frac{1}{4}+x\cdot\frac{1}{8}=\frac{21}{24}\)
\(x\cdot\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}\right)=\frac{7}{8}\)
\(x\cdot\frac{7}{8}=\frac{7}{8}\)
\(\Rightarrow x=\frac{7}{8}\div\frac{7}{8}=1\)
b) \(\left(x+4\right)+\left(x+9\right)+\left(x+14\right)+.....+\left(x+44\right)+\left(x+49\right)=1430\)
\(\left(x+x+x+....+x+x\right)+\left(4+9+14+...+44+49\right)=1430\)
\(10x+265=1430\)
\(10x=1430-265\)
\(10x=1165\)
\(\Rightarrow x=\frac{1165}{10}=116,5\)
c) \(x\cdot0,25-0,5=1\)
\(x\cdot0,25=1+0,5\)
\(x\cdot0,25=1,5\)
\(\Rightarrow x=1,5\div0,25=6\)
1/4.12/13+1/4.1/13-3/25
1/4.(12/13+1/13)-3/25
1/4.1-3/25
1/4-3/25
1/8
\(\frac{1}{4}\cdot\frac{12}{13}+\frac{1}{4}\cdot\frac{1}{13}-12\%=\frac{1}{4}\cdot\frac{12}{13}+\frac{1}{4}\cdot\frac{1}{13}-\frac{3}{25}=\frac{1}{4}\cdot\left(\frac{12}{13}+\frac{1}{13}\right)-\frac{3}{25}\)
\(=\frac{1}{4}\cdot1-\frac{3}{25}=\frac{1}{4}-\frac{3}{25}=\frac{13}{100}\)
Nhớ bài đây sửa đi sửa lại cũng vì do cái số " % " :(((
a) \(\left|\frac{2}{5}:x\right|=\frac{1}{4}\)
Trường hợp 1 : \(\frac{2}{5}\) : x = \(\frac{1}{4}\)
=> x = \(\frac{2}{5}:\frac{1}{4}=\frac{2}{5}\cdot4=\frac{8}{5}\)
Trường hợp 2 : \(\frac{2}{5}:x=-\frac{1}{4}\)
=> \(x=\frac{2}{5}:\left(-\frac{1}{4}\right)=\frac{2}{5}\cdot\left(-4\right)=-\frac{8}{5}\)
Vậy \(x=\pm\frac{8}{5}\)
b) \(\frac{x}{24}=-\frac{1}{3}-\frac{1}{8}=-\frac{11}{24}\)
=> x = -11
c) \(\frac{3}{x+3}=\frac{-7}{21}\)
=> \(\frac{3}{x+3}=\frac{-1}{3}\)
=> -1(x + 3) = 9
=> -x - 3 = 9
=> -x = 12
=> x = -12
`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`
__
`x:2/3=4/9`
`=>x=4/9xx2/3`
`=>x=8/27`
Vậy `x=8/27`
__
`x-1/4=3/2`
`=>x=3/2+1/4`
`=>x=6/4+1/4`
`=>x=7/4`
Vậy `x=7/4`
__
`x+4/5=8/9`
`=>x=8/9-4/5`
`=>x=40/45-36/45`
`=>x=4/45`
Vậy `x=4/45`
\(x\cdot\dfrac{6}{7}=\dfrac{5}{14}\)
\(x\) \(=\dfrac{5}{14}:\dfrac{6}{7}\)
\(x\) \(=\dfrac{5}{12}\)
\(x:\dfrac{2}{3}=\dfrac{4}{9}\)
\(x\) \(=\dfrac{4}{9}\cdot\dfrac{2}{3}\)
\(x\) \(=\dfrac{8}{27}\)
\(x-\dfrac{1}{4}=\dfrac{3}{2}\)
\(x\) \(=\dfrac{3}{2}+\dfrac{1}{4}\)
\(x\) \(=\dfrac{7}{4}\)
\(x+\dfrac{4}{5}=\dfrac{8}{9}\)
\(x\) \(=\dfrac{8}{9}-\dfrac{4}{5}\)
\(x\) \(=\dfrac{4}{45}\)
\(x\times\frac{1}{2}\)\(+x\times\frac{1}{4}\)\(+x\times\frac{1}{8}\)\(=\frac{21}{24}\)
\(x\times\frac{1}{2}\)\(+x\times\frac{1}{4}\)\(=\frac{21}{24}\)\(\div\frac{1}{8}\)
\(x\times\frac{1}{2}\)\(+x\times\frac{1}{4}\)\(=\frac{168}{24}\)
\(x\times\frac{1}{2}\)\(=\)\(\frac{168}{24}\div\frac{1}{4}\)
\(x\times\frac{1}{2}\)\(=\frac{1344}{24}\)
\(x=\frac{1344}{24}\div\frac{1}{2}\)
\(x=112\)
X x 1/2 + X x 1/4 + 1/8 x X = 21/24
X x ( 1/2 + 1/4 + 1/8 ) = 21/24
X x ( 4/8 + 2/8 + 1/8 ) = 21/24
X x 7/8 = 21/24
X = 21/24 : 7/8
X = 21/24 x 8/7
X = 168/168 = 1
X x 1/2+ X x 1/4 + 1/8 x X = 21/24
X x = 1/2 -1/4 - 1/8 =21/24
X x [4/8+ 2/8 + 1/8 = 21/24
X x 7/8 = 21/24
X = 21/24 : 7/8
X = 21/24 X8/7
x = 168/168 = 1