(x + 1/3) + (x + 1/9) + (x + 1/27 ) + ( x + 1/81) = 56/81
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ta có :
\(\frac{x+1}{3}+\frac{x+1}{9}+\frac{x+1}{27}+\frac{x+1}{81}=\left(x+1\right)\times\left(\frac{1}{3}+\frac{1}{9}+\frac{1}{27}+\frac{1}{81}\right)\)
\(=\left(x+1\right)\times\frac{40}{81}=\frac{56}{81}\text{ nên }x+1=\frac{56}{40}=\frac{7}{5}\)
vậy \(x=\frac{7}{5}-1=\frac{2}{5}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Tham khảo link: https://olm.vn/hoi-dap/detail/55111422944.html
`(x+1/3)+(x+1/9)+(x+1/27)+(x+1/81)=56/81`
`x+x+x+x+1/3+1/9+1/27=56/81-1/81`
`4x+13/27=55/81`
`4x=55/81-13/27`
`4x=55/81-52/81`
`4x=16/81`
`x=4/108`
Vậy `x=4/108`
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Bài 1:
$(y+\frac{1}{3})+(y+\frac{1}{9})+(y+\frac{1}{27})+(y+\frac{1}{81})=\frac{56}{81}$
$(y+y+y+y)+(\frac{1}{3}+\frac{1}{9}+\frac{1}{27}+\frac{1}{81})=\frac{56}{81}$
$4\times y+\frac{40}{81}=\frac{56}{81}$
$4\times y=\frac{56}{81}-\frac{40}{81}=\frac{16}{81}$
$y=\frac{16}{81}:4=\frac{4}{81}$
Bài 2:
$18: \frac{x\times 0,4+0,32}{x}+5=14$
$18: \frac{x\times 0,4+0,32}{x}=14-5=9$
$\frac{x\times 0,4+0,32}{x}=18:9=2$
$x\times 0,4+0,32=2\times x$
$2\times x-x\times 0,4=0,32$
$x\times (2-0,4)=0,32$
$x\times 1,6=0,32$
$x=0,32:1,6=0,2$
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a)= ( 81 , 6 x 27 , 3 – 17 , 3 x 81 , 6 ) x 0
=0 ( vì 0 nhân với số nào cũng bằng 0)
b)= ( 13 , 75 – 0 , 48 x 5 ) x ( 42 , 75 : 3 + 2 , 9 ) x ( 9-9)
= ( 13 , 75 – 0 , 48 x 5 ) x ( 42 , 75 : 3 + 2 , 9 ) x 0
= 0 ( vì 0 nhân với số nào cũng bằng 0)
c)=( 792 , 81 x 0 , 25 + 792 , 81 x 0 , 75 ) x 0
=0 ( vì 0 nhân với số nào cũng bằng 0 )
a ) ( 81 , 6 x 27 , 3 – 17 , 3 x 81 , 6 ) x ( 32 x 11 - 3200 x 0 , 1 - 32 )
= ( 81 , 6 x 27 , 3 – 17 , 3 x 81 , 6 ) x ( 352 - 320 - 32 )
= ( 81 , 6 x 27 , 3 – 17 , 3 x 81 , 6 ) x 0
= 0.
b ) ( 13 , 75 – 0 , 48 x 5 ) x ( 42 , 75 : 3 + 2 , 9 ) x ( 1 , 8 x 5 – 0 , 9 x 10 )
= ( 13 , 75 – 0 , 48 x 5 ) x ( 42 , 75 : 3 + 2 , 9 ) x ( 9 - 9 )
= ( 13 , 75 – 0 , 48 x 5 ) x ( 42 , 75 : 3 + 2 , 9 ) x 0
= 0
c ) ( 792 , 81 x 0 , 25 + 792 , 81 x 0 , 75 ) x ( 11 x 9 – 900 x 0 , 1 – 9 )
= ( 792 , 81 x 0 , 25 + 792 , 81 x 0 , 75 ) x ( 99 - 90 - 9 )
= ( 792 , 81 x 0 , 25 + 792 , 81 x 0 , 75 ) x 0
= 0.
Hok tốt !
![](https://rs.olm.vn/images/avt/0.png?1311)
\(x+1+\dfrac{1}{3}+\dfrac{1}{9}+\dfrac{1}{27}+\dfrac{1}{81}=2\)
\(\Leftrightarrow x+\dfrac{121}{81}=2\)
hay \(x=\dfrac{41}{81}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
(1/3+1/9+1/27+1/81)÷x=11/2
40/81 : x = 11/2
x= 40/81 : 11/2
x=80/891
Tim x
(1/3+1/9+1/27+1/81)÷x=11/2
(1/3+1/9+1/27+1/81)÷x=11/2
40/81 : x = 11/2
x= 40/81 : 11/2
x=80/891
\(\left(x+\dfrac{1}{3}\right)+\left(x+\dfrac{1}{9}\right)+\left(x+\dfrac{1}{27}\right)+\left(x+\dfrac{1}{81}\right)=\dfrac{56}{81}\)
\(\left(x+x+x+x\right)+\left(\dfrac{1}{3}+\dfrac{1}{9}+\dfrac{1}{27}+\dfrac{1}{81}\right)=\dfrac{56}{81}\)
\(4x+\dfrac{40}{81}=\dfrac{56}{81}\)
\(4x=\dfrac{56}{81}-\dfrac{40}{81}\)
\(4x=\dfrac{16}{81}\)
\(x=\dfrac{16}{81}:4\)
\(x=\dfrac{4}{81}\)
Vậy \(x=\dfrac{4}{81}\)
\(\left(x+\dfrac{1}{3}\right)+\left(x+\dfrac{1}{9}\right)+\left(x+\dfrac{1}{81}\right)=\dfrac{56}{81}\)
\(x+\dfrac{1}{3}+x+\dfrac{1}{9}+x+\dfrac{1}{27}+x+\dfrac{1}{81}=\dfrac{56}{81}\)
\(\left(x+x+x+x\right)+\left(\dfrac{1}{3}+\dfrac{1}{9}+\dfrac{1}{27}+\dfrac{1}{81}\right)=\dfrac{56}{81}\)
\(4\times x+\dfrac{40}{81}=\dfrac{56}{81}\)
\(4\times x=\dfrac{56}{81}-\dfrac{40}{81}\)
\(4\times x=\dfrac{16}{81}\)
\(x=\dfrac{16}{81}:4\)
\(x=\dfrac{4}{81}\)