(2,4.x-36):1 5/7=-1
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( 2,4 x - 36) : \(1\dfrac{5}{7}\) = -14
( \(\dfrac{12}{5}\) x - 36) : \(\dfrac{12}{7}\) = -14
( \(\dfrac{12}{5}\) x -36 ) = -14 . \(\dfrac{12}{7}\)
\(\dfrac{12}{5}\) x -36 = -24
\(\dfrac{12}{5}\) x = -24 + 36
\(\dfrac{12}{5}\) x = 12
x = 12 : \(\dfrac{12}{5}\)
x = 5
`1/7+(-9/27)+10/7+(-4/7)`
`= (1/7 + (-4)/7+10/7) +(-9/27)`
`= 7/7 +(-9/27)`
`= 1 +(-9/27)`
`= 27/27 + (-9/27)`
`=18/27`
`=2/3`
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`1,3 xx2 1/4 -1,3 xx3 1/4`
`= 1,3 xx 9/4 -1,3 xx 13/4`
`=1,3 xx (9/4-13/4)`
`=1,3xx(-4)/4`
`=1,3 xx (-1)`
`=-1,3`
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`1/4: x = 2,4 -4/5`
`=> 1/4 : x= 12/5 -4/5`
`=> 1/4 : x=8/5`
`=> x=1/4 : 8/5`
`=> x= 1/4 xx 5/8`
`=> x= 5/32`
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`5/4 ( x- 3/5)= -1/8`
`=> x-3/5 = -1/8 : 5/4`
`=> x-3/5 = -1/8 xx 4/5`
`=> x-3/5 =-4/40`
`=> x-3/5 =-1/10`
`=> x=-1/10 +3/5`
`=> x=-1/10 + 6/10`
`=> x= 5/10`
`=>x=1/2`
` @ yngoc`
\(\left(x\cdot2,4-4,2\right)\div x=1\)
\(\Rightarrow x\cdot2,4-4,2=x\)
\(\Rightarrow x\cdot2,4=x+4,2\)
\(\Rightarrow\frac{12x}{5}=\frac{5x+21}{5}\)
\(\Rightarrow12x=5x+21\)
\(\Rightarrow12x-5x=21\)
\(\Rightarrow7x=21\Rightarrow x=\frac{21}{7}=3\)
Vậy x = 3
\(\frac{1}{1\cdot3}+\frac{1}{3\cdot5}+...+\frac{1}{x\left(x+2\right)}\)
\(=\frac{1}{2}\cdot\left(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{x}-\frac{1}{x+2}\right)\)
\(=\frac{1}{2}\cdot\left(1-\frac{1}{x+2}\right)\)
\(=\frac{1}{2}\cdot\frac{x+1}{x+2}\)
\(=\frac{x+1}{2x+2}\)
a) \(\dfrac{3}{4}\times x:\dfrac{1}{2}=\dfrac{4}{5}\)
\(\dfrac{3}{4}\times x=\dfrac{4}{5}\times\dfrac{1}{2}\)
\(\dfrac{3}{4}\times x=\dfrac{2}{5}\)
\(x=\dfrac{2}{5}:\dfrac{3}{4}\)
\(x=\dfrac{8}{15}\)
b) \(\left(14-x:6\right)\times7=84\)
\(14-x:6=84:7\)
\(14-x:6=12\)
\(x:6=14-12\)
\(x:6=2\)
\(x=6\times2=12\)
c) \(x\times1,5:2,4=0,3\)
\(x\times1,5=0,3\times2,4\)
\(x\times1,5=0,72\)
\(x=0,72:1,5\)
\(x=0,48\)
d) Thiếu x
9: =>x-3=2
=>x=5
10: =>x+1/2=1/5 hoặc x+1/2=-1/5
=>x=-7/10 hoặc x=-3/10
12:
a: =>x^2=900
=>x=30 hoặc x=-30
b: =>x=1/18*27=3/2
7: =>|x-0,4|=1,1
=>x-0,4=1,1 hoặc x-0,4=-1,1
=>x=1,5 hoặc x=-0,7
\(a,5,2x+7\dfrac{2}{5}=6\dfrac{3}{4}\\ \Rightarrow\dfrac{26}{5}x+\dfrac{37}{5}=\dfrac{27}{4}\\ \Rightarrow\dfrac{26}{5}x=-\dfrac{13}{20}\\ \Rightarrow x=-\dfrac{1}{8}\\ b,2,4:\left(\dfrac{-1}{2}-x\right)=1\dfrac{3}{5}\\ \Rightarrow\dfrac{12}{5}:\left(\dfrac{-1}{2}-x\right)=\dfrac{8}{5}\\ \Rightarrow\dfrac{-1}{2}-x=\dfrac{3}{2}\\ \Rightarrow x=-2\)