( x + 1/2 ) + ( x + 1/4 ) + ( x + 1/8 ) + ( x + 1/16 ) = 31/16
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\(\left(x+\frac{1}{2}\right)+\left(x+\frac{1}{4}\right)+\left(x+\frac{1}{8}\right)+\left(x+\frac{1}{16}\right)=1\)
\(x+x+x+x+\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}\right)=1\)
\(4x+\frac{15}{16}=1\)
\(4x=1-\frac{15}{16}\)
\(4x=\frac{1}{16}\)
\(x=\frac{1}{16}\div4\)
\(x=\frac{1}{64}\)
ta coi x để ra mội bên ta có 1/2 + 1/4 + 1/8 + 1/6 = 25/24
x + 25/24 = 1
x = 1 - 25/24
x = -1/24
mk nha
\(\left(1-x\right)\left(1+x+x^2+...+x^{31}\right)=1-x^{32}\)
\(\left(1-x\right)\left(1+x\right)\left(1+x^2\right)\left(1+x^4\right)\left(1+x^8\right)\left(1+x^{16}\right)\)
\(=\left(1-x^2\right)\left(1+x^2\right)\left(1+x^4\right)\left(1+x^8\right)\left(1+x^{16}\right)\)
\(=\left(1-x^4\right)\left(1+x^4\right)\left(1+x^8\right)\left(1+x^{16}\right)\)
\(=\left(1-x^8\right)\left(1+x^8\right)\left(1+x^{16}\right)\)
\(=\left(1-x^{16}\right)\left(1+x^{16}\right)\)
\(=1-x^{32}\)
Ta có đpcm.
Đk x khác 0
pt <=> 1.3+1/1.3 . 2.4+1/2.4 . ...... . x.(x+2)+1/x.(x+2) = 31/16
<=> 2^2/1.3 . 3^2/2.4 . ...... . (x+1)^2/x.(x+2) = 31/16
<=> 31/16 = 2^2.3^3. .... .(x+1)^2/1.3.2.4. .... .x.(x+2)
= 2.3. ..... .(x+1)/1.2. .... .x . 2.3. .... . (x+1)/3.4. .... .(x+2)
= (x+1).2/(x+2)
<=> x+1/x+2 = 31/16 : 2 = 31/32 = 30+1/30+2
<=> x = 30
Vậy ..............
Tk mk nha
2/5 + 11/15 = 17/15
7/8 - 7/9 = 7/72
11/13 x 26/31 = 22/31
16/24 : 4 = 1/6
30 : 6/5 = 25
9/16 : 4 = 9/64
1/2 : 1/3 x 8/15 = 3/2 x 8/15 = 4/5
a, \(\dfrac{x+2}{2}=\dfrac{6}{12}\Rightarrow6x+12=6\Leftrightarrow x=-1\)
b, đk : x khác 1
\(\dfrac{8}{x-1}=-\dfrac{16}{22}=-\dfrac{8}{11}\Rightarrow x-1=-11\Leftrightarrow x=-10\)(tm)
3/2+5/4+9/8/+17/16+33/32-6+x-1/x+1=31/32-2/2015
=(1+1/2)+(1+1/4)+(1+1/8)+(1+1/16)+(1+1/32-6+x-1/x+1=31/32-2/2015
=(1/2+1/4+1/8+1/16+1/32)+(1+1+1+1+1)-6+x-1/x+1=31/32-2/2015
=31/32+5-6+x-1/x+1=31/32-2/2015
=5-6+x-1/x+1=31/32-2/2015-31/32
=-1+x-1/x+1=-2/2015
=x-1/x+1=-2/2015- -1
=x-1/x+1=2013/2015
=>x=2014
a: =7/8:(2/9-18+1/36)-5/12
=-7/142-5/12=-397/852
b: =3/7(4/9+5/9:6/12)=2/3
c: =5^8(16/31-47/31)+1/3=-5^8+1/3
d: =7/2(3/8+5/8:4/15)=609/64
\(\left(x+\dfrac{1}{2}\right)+\left(x+\dfrac{1}{4}\right)+\left(x+\dfrac{1}{8}\right)+\left(x+\dfrac{1}{16}\right)=\dfrac{31}{16}\\ x+\dfrac{1}{2}+x+\dfrac{1}{4}+x+\dfrac{1}{8}+x+\dfrac{1}{16}=\dfrac{31}{16}\\ \left(x+x+x+x\right)+\left(\dfrac{1}{2}+\dfrac{1}{4}+\dfrac{1}{8}+\dfrac{1}{16}\right)=\dfrac{31}{16}\\ x\times\left(1+1+1+1\right)+\left(\dfrac{8}{16}+\dfrac{4}{16}+\dfrac{2}{16}+\dfrac{1}{16}\right)=\dfrac{31}{16}\\ x\times4+\dfrac{15}{16}=\dfrac{31}{16}\\ x\times4=\dfrac{31}{16}-\dfrac{15}{16}\\ x\times4=\dfrac{16}{16}\\ x\times4=1\\ x=1:4\\ x=\dfrac{1}{4}\)
Ai nhanh nhất mình đúng cho