đcm là đầu cắt moi

vì quá dễ nên mình không thể trả lời bạn được nhé!

dễ vl ko làm đc là ngu 

a.1025

mk chịu câu b

*** mk nha

                    Đặt \(A=\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}+\frac{1}{128}+\frac{1}{256}\)

                    \(A=\frac{1}{2^3}+\frac{1}{2^4}+\frac{1}{2^5}+\frac{1}{2^6}+\frac{1}{2^7}+\frac{1}{2^8}\)

                \(2A=\frac{1}{2^2}+\frac{1}{2^3}+\frac{1}{2^4}+\frac{1}{2^5}+\frac{1}{2^6}+\frac{1}{2^7}\)

               \(2A-A=\left(\frac{1}{2^2}+\frac{1}{2^3}+\frac{1}{2^4}+\frac{1}{2^5}+\frac{1}{2^6}+\frac{1}{2^7}\right)-\left(\frac{1}{2^3}+\frac{1}{2^4}+\frac{1}{2^5}+\frac{1}{2^6}+\frac{1}{2^7}+\frac{1}{2^8}\right)\)

              \(A=\frac{1}{2^2}-\frac{1}{2^8}\)

           \(A=\frac{1}{4}-\frac{1}{256}=\frac{63}{256}\)

          \(\Rightarrow\frac{63}{256}.x=\frac{1}{512}=\frac{1}{2^9}\)

           \(\Rightarrow\frac{63}{2^8}.x=\frac{1}{2^9}\)

            \(\Rightarrow x=\frac{1}{2^9}:\frac{63}{2^8}=\frac{1}{2^9}.\frac{2^8}{63}=\frac{1}{2.63}=\frac{1}{126}\)

           Ủng hộ mk nha !!! ^_^

13,44 . x - (1,6 + x) . 0,5 - 3,7 . (x - 0,9) =13,618

=> 13,44x - 0,8 - 0,5x - 3,7x + 3,33 - 13,618 = 0

=> 9,24x - 11,088 = 0

=> 9,24x = 11,088

=> x = 1,2

13,44 . x - (1,6 + x) . 0,5 - 3,7 . (x - 0,9) =13,618

=> 13,44x - 0,8 - 0,5x - 3,7x + 3,33 - 13,618 = 0

=> 9,24x - 11,088 = 0

=> 9,24x = 11,088

=> x = 1,2

13,44 . x - (1,6 + x) . 0,5 - 3,7 . (x - 0,9) =13,618

=> 13,44x - 0,8 - 0,5x - 3,7x + 3,33 - 13,618 = 0

=> 9,24x - 11,088 = 0

=> 9,24x = 11,088

=> x = 1,2

 A = 1/2 + 1/4 + 1/8 + ... + 1/1024

2A = 1 + 1/2 + 1/4 + ... + 1/512

2A - A = (1 + 1/2 + 1/4 + ... + 1/512) - (1/2 + 1/4 + 1/8 + ... + 1/1024)

A = 1 - 1/1024

A = 1023/1024

\(A=\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+....+\frac{1}{1024}\)

\(\Rightarrow2A=1+\frac{1}{2}+\frac{1}{4}+......+\frac{1}{512}\)

\(\Rightarrow A=2A-A=1-\frac{1}{1024}\)

\(A=\frac{1023}{1024}\)

A=\(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+...+\frac{1}{512}+\frac{1}{1024}\)

2 x A=\(1+\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+...+\frac{1}{512}\)

2 x A - A = \(\left(1+\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+...+\frac{1}{512}\right)-\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+...+\frac{1}{512}+\frac{1}{1024}\right)\)

A=\(1-\frac{1}{1024}\)

A=\(\frac{1023}{1024}\)

1. 2006/987654321 + 2007/246813579 = 2007/246813579 + 2006/987654321

=>

2.

3 - (5.3/8 + X - 7 . 5/24) : 6 . 2/3 =2

3 - (15/8 + X - 35/24) : 4 = 2

3 - (15/8 + X - 35/24) = 2 . 4

3 - (15/8 + X - 35/24) = 8

15/8 + X - 35/24 = 3 - 8

15/8 + X - 35/24 = -5

15/8 + X = -5 + 35/24

15/8 + X = -85/24

X = -85/24 - 15/8

X = -65/12

Chính xác không bạn

\(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}+\frac{1}{128}+\frac{1}{256}\)

\(< =>\frac{128}{256}+\frac{64}{256}+\frac{32}{256}+\frac{16}{256}+\frac{8}{256}+\frac{4}{256}+\frac{2}{256}+\frac{1}{256}\)

\(< =>\frac{128+64+32+16+8+4+2+1}{256}\)

\(< =>\frac{255}{256}\)

\(\frac{1}{1\cdot2}+\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+...+\frac{1}{99\cdot100}\)

\(< =>\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{99}-\frac{1}{100}\)

\(< =>\frac{1}{1}-\frac{1}{100}\)

\(< =>\frac{99}{100}\)

\(\left(1-\frac{1}{2}\right)\cdot\left(1-\frac{1}{3}\right)\cdot\left(1-\frac{1}{4}\right)\cdot...\cdot\left(1-\frac{1}{100}\right)\)

\(< =>\frac{1}{2}\cdot\frac{2}{3}\cdot\frac{3}{4}\cdot...\cdot\frac{99}{100}\)

\(< =>\frac{1\cdot2\cdot3\cdot...\cdot99}{2\cdot3\cdot4\cdot...\cdot100}\)

\(< =>\frac{1}{100}\)

mk chuc ban hoc tot nhe :))

NÔNNO

a) \(\frac{37-2\times\left(y-3,25\right)}{5}=7,06\)

=> \(37-2\times\left(y-3,25\right)=7,06\times5\)

=> \(37-2\times\left(y-3,25\right)=35,3\)

=> \(2\times\left(y-3,25\right)=37-35,3=1,7\)

=> \(y-3,25=1,7:2=0,85\)

=> y = 0,85 + 3,25 = 4,1

Tới khúc này là dẫn đến tìm x chứ không tìm y nx ...

Sửa câu b lại đi

c) \(\frac{5}{12}\times\left(8+x\right)-\frac{1}{5}\times\left(\frac{15}{4}+x\right)=15\)

=> \(\frac{10}{3}+\frac{5}{12}x-\frac{3}{4}+\frac{1}{5}x=15\)

=> \(\left(\frac{10}{3}-\frac{3}{4}\right)-\left(\frac{5}{12}x-\frac{1}{5}x\right)=15\)

=> \(\frac{31}{12}+\frac{13}{60}x=15\)

=> \(\frac{13}{60}x=15-\frac{31}{12}=\frac{149}{12}\)

=> \(x=\frac{149}{12}:\frac{13}{60}=\frac{149}{12}\cdot\frac{60}{13}=\frac{745}{13}\)

Làm nốt câu d nhé 

= (64/256 + 32/256 + 16/256 + 8/256 + 4/256 + 2/256) X x =1

= 126 X x = 1

x = 1 : 126

x= 1/126

nhớ k mình nha !!!