\(2x+1+\frac{1}{6}+1+\frac{1}{12}+..+1+\frac{1}{90}=10\)

=> 2x + 8 + \(\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{9.10}=10\)

=> 2x + \(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{9}-\frac{1}{10}=10-8\)

\(2x+1-\frac{1}{10}=2\)

=> 2x + \(\frac{9}{10}=2\)

=> 2x          = 2 - 9/10

=>2x           = 11/10 

=> x              = 11/10 : 2

x                  =  11/20 

thang Tran ơi,2x+1-1/10 ở đâu vậy

Phải là 2x+1/2-1/10 chứ

mk giải cho nè nhớ tích nha

2x+7/6+13/12+21/20+31/30+43/42+57/56+73/72+91/90=10

2x+(1/6+1)+(1/12+1)+(1/20+1)+(1/30+1)+(1/42+1)+(1/56+1)+(1/72+1)+(1/90+1)=10

2x+(1+1+1+1+1+1+1+1)+(1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90)=10

2x+8+(1/2+3+1/3+4+1/4+5+1/5+6+1/6+7+1/7+8+1/8+9+1/9+10)=10

2x+8+(1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10)=10

2x+8+(1/2-1/10)=10

2x+8+2/5=10

2x=10-8-2/5

2x=1,6

x=1,6:2

x=0,8

Mk thấy đề bài hơi dư nên x mk tìm ra là số thập phân còn đổi lại ra phân số là 4/5

\(\frac{-21}{5}\)

x= -127/30 .

gợi ý các bạn chọn ( k) đúng cho mình 

2x+7/6+13/12+21/20+31/30+43/42+57/56+73/72+91/90=10

2x+1+1/6+1+1/12+1+1/20+1+1/30+1+1/42+1+1/56+1+1/72+1+1/90=10

2x+(1+1+1+1+1+1+1+1)+(1/2.3+1/3.4+1/4.5+1/5.6+1/6.7+1/7.8+1/8.9+1/9.10)=10

2x+8+(1-1/2+1/2-1/3+...+1/9-1/10)=10

2x+1-1/10=10-8

2x+9/10=2

2x=2-9/10

2x=11/10

x=11/10/2

x=11/20

đáp án là 4/5

a) (x - 78) .26 = 0 => x - 78 = 0 => x = 78

b) 39 (x - 5) = 39 => x - 5 = 1 => x = 6

c) (x - 14) : 2 = 3 => x - 14 = 6 => x = 20

d) (30 - x) . 4 = 92 

=> 30 - x = 92 : 4 

=> 30 - x = 23

=> x = 30 - 23 = 7

e) 45(91 - x) = 90

=> 91 - x = 90 : 45

=> 91 - x = 2

=> x = 91 - 2 = 89

f) (2x - 6)(3x - 18) = 0

=> \(\orbr{\begin{cases}2x-6=0\\3x-18=0\end{cases}}\Rightarrow\orbr{\begin{cases}x=3\\x=6\end{cases}}\)

g) 5x + 73.21 = 73.26

=> 5x = 73.26 - 73.21

=> 5x = 73(26 - 21) = 73.5

=> x = \(\frac{73\cdot5}{5}=73\)

h) 2x - 12 - x = 0

=> 2x - x - 12 = 0

=> x - 12 = 0

=> x = 12

làm rõ giùmnha

làm rõ giùm mình với

\(2x+\frac{7}{6}+\frac{13}{12}+\frac{21}{20}+\frac{31}{30}+\frac{43}{42}+\frac{57}{56}+\frac{73}{72}+\frac{91}{90}=10\)
=> \(2x+\frac{6+1}{6}+\frac{12+1}{12}+....+\frac{90+1}{90}=10\)
=> \(2x+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{90}+10=10\)
=> \(2x+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{90}=0\)
=>\(2x+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{9.10}=0\)
=>\(2x+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{9}-\frac{1}{10}=0\)
=> \(2x-\frac{1}{10}=0\)
=>2x=\(\frac{1}{10}\)=> x=1/20
 

mình có bị nhầm chỗ dấu suy ra thứ 3. đáng lẽ ra biểu thức đó cộng 8 chứ k phải cộng 10 do mình sơ ý nên bạn hãy sủa lại chỗ ấy

đây nhá tại đánh máy lâu quá nên gửi hình ^^

a) \(\left(2x-6\right)\left(3x-18\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}2x-6=0\\3x-18=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=3\\x=6\end{cases}}\)

b) \(5x+73.21=73.26\)

\(\Leftrightarrow5x=73.5\)

\(\Rightarrow x=73\)

c) \(2x-12-x=0\)

\(\Rightarrow x=12\)

nhanh giúp mình nha

a) \(\left(2x-6\right)\left(3x-18\right)=0\Leftrightarrow\orbr{\begin{cases}2x-6=0\Leftrightarrow x=3\\3x-18=0\Leftrightarrow x=6\end{cases}}\)

b) \(5x+73.21=73.26\Leftrightarrow5x+73.21=5.75+73.21\Leftrightarrow x=5\)

b) \(2x-12-x=0\Leftrightarrow2x-x=x=12\)

\(2x+\dfrac{7}{6}+\dfrac{13}{12}+\dfrac{21}{20}+\dfrac{31}{30}+\dfrac{43}{42}+\dfrac{57}{56}+\dfrac{73}{72}+\dfrac{91}{90}=10\)

\(2x+\left(1+\dfrac{1}{6}\right)+\left(1+\dfrac{1}{12}\right)+\left(1+\dfrac{1}{20}\right)+\left(1+\dfrac{1}{30}\right)+\left(1+\dfrac{1}{42}\right)+\left(1+\dfrac{1}{56}\right)+\left(1+\dfrac{1}{72}\right)+\left(1+\dfrac{1}{90}\right)=10\)

\(2x+8+\left(\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}+\dfrac{1}{42}+\dfrac{1}{56}+\dfrac{1}{72}+\dfrac{1}{90}\right)=10\)

\(2x+8+\left(\dfrac{1}{2.3}+\dfrac{1}{3.4}+\dfrac{1}{4.5}+\dfrac{1}{5.6}+\dfrac{1}{6.7}+\dfrac{1}{7.8}+\dfrac{1}{8.9}+\dfrac{1}{9.10}\right)=10\)

\(2x+8+\left(\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{6}+\dfrac{1}{6}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{8}+\dfrac{1}{8}-\dfrac{1}{9}+\dfrac{1}{9}-\dfrac{1}{10}\right)=10\)

\(2x+8+\left(\dfrac{1}{2}-\dfrac{1}{10}\right)=10\)

~ Chúc bạn học tốt ~

2x+\(\dfrac{7}{2.3}+\dfrac{13}{3.4}+\dfrac{21}{4.5}+...+\dfrac{91}{9.10}=10\)

\(2x+7\left(\dfrac{1}{2.3}\right)+13\left(\dfrac{1}{3.4}\right)+...+91\left(\dfrac{1}{9.10}\right)=10\)

\(2x+\left(7+13+...+91\right)\left(\dfrac{1}{2.3}+\dfrac{1}{3.4}+...+\dfrac{1}{9.10}\right)=10\)

\(2x+336+\left(\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{9}-\dfrac{1}{10}\right)=10\)

\(2x+336+\left(\dfrac{1}{2}-\dfrac{1}{10}\right)=10\)

\(2x+336.\dfrac{2}{5}=10\)

\(2x+\dfrac{672}{5}=10\)

\(2x=10-\dfrac{672}{5}\)

\(2x=-\dfrac{622}{5}\)

\(x=-\dfrac{311}{5}\)

Tick nha 0o0^^^Nhi^^^0o0