a) 91 - x = 90
b) x - 73 . 21 = 73 . 26
c) 6 . ( x +11 ) = 0
d) 2x - 12 - x = 9
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PT
3
13 tháng 8 2015
\(2x+1+\frac{1}{6}+1+\frac{1}{12}+..+1+\frac{1}{90}=10\)
=> 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
EC
2
NN
2
16 tháng 7 2016
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
NQ
0
18 tháng 8 2020
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
11 tháng 7 2018
\(2x+\frac{7}{6}+\frac{13}{12}+\frac{21}{20}+\frac{31}{30}+\frac{43}{42}+\frac{57}{56}+\frac{73}{72}+\frac{91}{90}=10\)
=> \(2x+\frac{6+1}{6}+\frac{12+1}{12}+....+\frac{90+1}{90}=10\)
=> \(2x+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{90}+10=10\)
=> \(2x+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{90}=0\)
=>\(2x+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{9.10}=0\)
=>\(2x+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{9}-\frac{1}{10}=0\)
=> \(2x-\frac{1}{10}=0\)
=>2x=\(\frac{1}{10}\)=> x=1/20
11 tháng 7 2018
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
HT
5
NC
18 tháng 8 2020
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) \(2x-12-x=0\)
\(\Rightarrow x=12\)
Q
15 tháng 4 2017
\(2x+\dfrac{7}{6}+\dfrac{13}{12}+\dfrac{21}{20}+\dfrac{31}{30}+\dfrac{43}{42}+\dfrac{57}{56}+\dfrac{73}{72}+\dfrac{91}{90}=10\)
\(2x+\left(1+\dfrac{1}{6}\right)+\left(1+\dfrac{1}{12}\right)+\left(1+\dfrac{1}{20}\right)+\left(1+\dfrac{1}{30}\right)+\left(1+\dfrac{1}{42}\right)+\left(1+\dfrac{1}{56}\right)+\left(1+\dfrac{1}{72}\right)+\left(1+\dfrac{1}{90}\right)=10\)
\(2x+8+\left(\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}+\dfrac{1}{42}+\dfrac{1}{56}+\dfrac{1}{72}+\dfrac{1}{90}\right)=10\)
\(2x+8+\left(\dfrac{1}{2.3}+\dfrac{1}{3.4}+\dfrac{1}{4.5}+\dfrac{1}{5.6}+\dfrac{1}{6.7}+\dfrac{1}{7.8}+\dfrac{1}{8.9}+\dfrac{1}{9.10}\right)=10\)
\(2x+8+\left(\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{6}+\dfrac{1}{6}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{8}+\dfrac{1}{8}-\dfrac{1}{9}+\dfrac{1}{9}-\dfrac{1}{10}\right)=10\)
\(2x+8+\left(\dfrac{1}{2}-\dfrac{1}{10}\right)=10\)
~ Chúc bạn học tốt ~
15 tháng 4 2017
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
a) 91 - x = 90
x = 91 - 90
x = 1
b) x - 73.21 = 73.26
x = 73.26 + 73.21
x = 73.(26 + 21)
x = 73.47
x = 3431
c) 6.(x + 11) = 0
x + 11 = 0 : 6
x + 11 = 0
x = 0 - 11
x = -11
d) 2x - 12 - x = 9
=> 2x - (12 + 9) = x
=> (2 - 1)x = 21
=> x = 21
a)x=1
b)x=3431
c)x=-11
d)x=21