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PM
2
7 tháng 6 2018
\(A\times\left(1-\frac{1}{4}\right)\times\left(1-\frac{1}{9}\right)\times\left(1-\frac{1}{16}\right)\times\left(1-\frac{1}{25}\right)=\frac{8}{5}\)
\(A\times\frac{3}{2\times2}\times\frac{2\times4}{3\times3}\times\frac{3\times5}{4\times4}\times\frac{4\times6}{5\times5}=\frac{8}{5}\)
\(A\times\frac{3\times2\times4\times3\times5\times4\times6}{2\times2\times3\times3\times4\times4\times5\times5}=\frac{8}{5}\)
\(A\times\frac{6}{2\times5}=\frac{8}{5}\)
\(A\times\frac{3}{5}=\frac{8}{5}\)
\(A=\frac{8}{5}:\frac{3}{5}\)
\(A=\frac{8}{3}\)
7 tháng 6 2018
ta có:
A = 8/5 : [(1 - 1/4) x ... x (1 - 1/5)]
= 8/5 : [3/4 x 8/9 x 15/16 x 24/25]
= 8/5 : 3/5
= 8/5 x 5/3
= 8/3
... là như đề bài nha!
DD
Đoàn Đức Hà
Giáo viên
3 tháng 6 2021
\(A=\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}+\frac{1}{128}\)
\(2\times A=1+\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}\)
\(2\times A-A=\left(1+\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}\right)-\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}+\frac{1}{128}\right)\)
\(A=1-\frac{1}{128}\)
\(A=\frac{127}{128}\)
DD
Đoàn Đức Hà
Giáo viên
3 tháng 6 2021
\(B=\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}\)
\(2\times B=1+\frac{1}{2}+\frac{1}{4}+\frac{1}{8}\)
\(B=1-\frac{1}{16}=\frac{15}{16}\)
\(\left(x+\frac{1}{2}\right)+\left(x+\frac{1}{4}\right)+\left(x+\frac{1}{8}\right)+\left(x+\frac{1}{16}\right)=1\)
\(\Leftrightarrow4\times x+\frac{15}{16}=1\)
\(\Leftrightarrow4\times x=\frac{1}{16}\)
\(\Leftrightarrow x=\frac{1}{64}\)
YC
15 tháng 4 2021
Bài 2:
a,4x25x0,25x\(\frac{1}{5}\) x \(\frac{1}{2}\) x 2
=4x25x0,25x0,2x0,5x2
=(4x0,25)+(25x0,2)+(0,5x2)
= 1 + 5 1
=7
15 tháng 4 2021
X + 1/2 + X + 1/4 + X + 1/8 + X + 1/8 +X +1/16
= X + 8/16 + X + 4/16 + X + 2/16 + X + 2/16 +X + 1/16
= X + ( 8/16 + 4/16 + 2/16 + 2/16 ) + X +1/16
= X + 1 + X + 1/16
= X + ( 1 + 1/16 )
= X + 1 VÀ 1/16
SL
1
LV
9 tháng 12 2015
4x + 1/2 + 1/4 + 1/8 + 1/16 =1
4x +15/16= 1
4x = 1 - 15/16
4x = 1/16
x = 1/64
Q
29 tháng 4 2016
(x+1/2)+(x+1/4)+(x+1/8)+(x+1/16)=1
(x+x+x+x)+(1/2+1/4+1/8+1/16)=1
4x+(1/2+1/4+1/8+1/16)=1
4x+15/16=1
4x=1-15/16
4x=1/16
x=1/16:4
x=1/64
29 tháng 4 2016
(x+1/2)+(x+1/4)+(x+1/8)+(x+1/16)=1
(x+x+x+x)+(1/2+1/4+1/8+1/16)=1
4x+(1/2+1/4+1/8+1/16)=1
4x+15/16=1
4x=1-15/16
4x=1/16
x=1/16:4
x=1/64
(\(x\) + 1) + (\(x\) + \(\dfrac{1}{2}\)) + (\(x\) + \(\dfrac{1}{4}\)) + (\(x\) + \(\dfrac{1}{8}\)) + (\(x\) + \(\dfrac{1}{16}\)) = \(\dfrac{25}{8}\)
\(x\) + 1 + \(x\) + \(\dfrac{1}{2}\) + \(x\) + \(\dfrac{1}{4}\) + \(x\) + \(\dfrac{1}{8}\) + \(x\) + \(\dfrac{1}{16}\) = \(\dfrac{25}{8}\)
(\(x\) + \(x\) + \(x\) + \(x\) + \(x\) ) + (1 + \(\dfrac{1}{2}\) + \(\dfrac{1}{4}\) + \(\dfrac{1}{8}\) + \(\dfrac{1}{16}\)) = \(\dfrac{25}{8}\)
\(x\) \(\times\) (1 + 1 + 1 + 1 + 1) + (\(\dfrac{16}{16}\) + \(\dfrac{8}{16}\) + \(\dfrac{4}{16}\) + \(\dfrac{2}{16}\) + \(\dfrac{1}{16}\) )= \(\dfrac{50}{16}\)
\(x\) \(\times\) 5 + \(\dfrac{31}{16}\) = \(\dfrac{50}{16}\)
\(x\) \(\times\) 5 = \(\dfrac{50}{16}\) - \(\dfrac{31}{16}\)
\(x\) \(\times\) 5 = \(\dfrac{19}{16}\)
\(x\) = \(\dfrac{19}{16}\) : 5
\(x\) = \(\dfrac{19}{80}\)
\(\left(x+1\right)+\left(x+\dfrac{1}{2}\right)+\left(x+\dfrac{1}{4}\right)+\left(x+\dfrac{1}{8}\right)+\left(x+\dfrac{1}{6}\right)=\dfrac{25}{8}\)
\(\left(x+x+x+x+x\right)+\left(1+\dfrac{1}{2}+\dfrac{1}{4}+\dfrac{1}{8}+\dfrac{1}{16}\right)=\dfrac{25}{8}\)
\(x\times5+\left(\dfrac{16}{16}+\dfrac{8}{16}+\dfrac{4}{16}+\dfrac{2}{16}+\dfrac{1}{16}\right)=\dfrac{25}{8}\)
\(x\times5+\dfrac{31}{16}=\dfrac{50}{16}\)
\(x\times5=\dfrac{50}{16}-\dfrac{31}{16}\)
\(x\times5=\dfrac{19}{16}\)
\(x=\dfrac{19}{16}:5\)
\(x=\dfrac{19}{16}\times\dfrac{1}{5}=\dfrac{19}{80}\)