7/9 : (2 + 3/4x) +5/9 = 23/27
tìm x nha các bạn
K
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17 tháng 8 2016
\(\frac{2}{3\times5}+\frac{2}{5\times7}+\frac{2}{7\times9}+...+\frac{2}{21\times23}\)
\(=\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+...+\frac{1}{21}-\frac{1}{23}\)
\(=\frac{1}{3}-\frac{1}{23}\)
\(=\frac{20}{69}\)
6 tháng 2 2019
a) \(\left(8x+5\right)^2\left(4x+3\right)\left(2x+1\right)=9\)
\(\Leftrightarrow\left(64x^2+8x+25\right)\left(8x^2+10x+3\right)-9=0\)
Đặt a = \(8x^2+10x+3\)
\(\left(8a+1\right)a-9=0\)
\(\Leftrightarrow8a^2+a-9=0\)
\(\Leftrightarrow\left(a-1\right)\left(8a+9\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}a=1\\a=-\frac{9}{8}\end{cases}}\)\(\Leftrightarrow\orbr{\begin{cases}8x^2+10x+3=1\\8x^2+10x+3=-\frac{9}{8}\end{cases}}\)
mà \(8x^2+10x+3=1\Rightarrow8x^2+10x+2=0\)
\(\Rightarrow2\left(x+1\right)\left(4x+1\right)=0\)
\(\Rightarrow\orbr{\begin{cases}x=-1\\x=-0,25\end{cases}}\)
VN
23 tháng 1 2017
Làm 1,2 câu thôi nhé :(
1)
<=> 4x - 20 - 3x - 21 = 5 + 4
<=> 4x - 3x = 5 + 4 + 20 + 21
<=> x = 50
2)
<=> 20 - 5x + 7x - 14 = -2
<=> 2x = -2 - 20 + 14
<=> 2x = -8
<=> x = -8 : 2
<=> x = -4
Các câu sau tươg tự nha
N
3
15 tháng 4 2019
7/9:(2+3/4x)=23/27-5/9
7/9:(2+3/4x)=8/27
2+3/4x=7/9:8/27
2+3/4x=21/8
3/4x=21/8-2
3/4x=5/8
x=5/8:3/4
x=5/6
KN
15 tháng 4 2019
\(\frac{7}{9}:\left(2+\frac{3}{4}x\right)+\frac{5}{9}=\frac{23}{27}\)
\(\Rightarrow\left(2+\frac{3}{4}x\right)+\frac{5}{9}=\frac{7}{9}:\frac{23}{27}=\frac{21}{23}\)
\(\Rightarrow2+\frac{3}{4}x=\frac{21}{23}-\frac{5}{9}=\frac{74}{207}\)
\(\Rightarrow\frac{3}{4}x=2-\frac{74}{207}=\frac{340}{207}\)
\(\Rightarrow x=\frac{340}{207}:\frac{3}{4}\)
\(\Rightarrow x=\frac{1360}{621}\)
25 tháng 4 2016
7/9 : ( 2 + 3/4 x) + 5/9 = 23/27
7/9 : ( 2 + 3/4 x) = 23/27 - 5/9 = 8/27
2 + 3/4 x= 7/9 : 8/27 = 21/8
3/4x = 21/8 - 2 = 5/8
=> x = 5/8 : 3/4 = 5/6
A
1
18 tháng 7 2017
a,x.3\(\dfrac{1}{4}\)+(\(\dfrac{-7}{6}\)).x-1\(\dfrac{2}{3}\)=\(\dfrac{5}{12}\)
\(\Leftrightarrow\)\(\dfrac{13}{4}\)x+(\(\dfrac{-7}{6}\))x-\(\dfrac{5}{3}\)=\(\dfrac{5}{12}\)
\(\Leftrightarrow\)\(\dfrac{13}{4}\)x+(\(\dfrac{-7}{6}\))x=\(\dfrac{25}{12}\)
\(\Leftrightarrow\)\(\dfrac{25}{12}\)x=\(\dfrac{25}{12}\)
\(\Leftrightarrow\)x=1
Vậy x=1
b,\(\dfrac{2}{5}\)+\(\dfrac{3}{5}\).(3x-3,7)=\(\dfrac{-53}{10}\)
\(\Leftrightarrow\)\(\dfrac{3}{5}\).(3x-3,7)=\(\dfrac{-53}{10}\)-\(\dfrac{2}{5}\)
\(\Leftrightarrow\)\(\dfrac{9}{5}\)x-\(\dfrac{111}{50}\)=\(\dfrac{-57}{10}\)
\(\Leftrightarrow\)\(\dfrac{9}{5}\)x=\(\dfrac{-87}{25}\)
\(\Leftrightarrow\)x=\(\dfrac{-29}{15}\)
Vậy x=\(\dfrac{-29}{15}\)
c,\(\dfrac{7}{9}\):(2+\(\dfrac{3}{4}\)x)+\(\dfrac{5}{9}\)=\(\dfrac{23}{27}\)
\(\Leftrightarrow\)\(\dfrac{7}{9}\):(2+\(\dfrac{3}{4}\)x)=\(\dfrac{8}{27}\)
\(\Leftrightarrow\)\(\dfrac{7}{18}\)+\(\dfrac{28}{27}\)x=\(\dfrac{8}{27}\)
\(\Leftrightarrow\)\(\dfrac{28}{27}\)x=\(\dfrac{-5}{54}\)
\(\Leftrightarrow\)x=\(\dfrac{-5}{56}\)
Vậy x=\(\dfrac{-5}{56}\)
\(\frac{7}{9}:\left(1+\frac{3}{4}x\right)+\frac{5}{9}=\frac{23}{27}\)
\(\frac{7}{9}:\left(1+\frac{3}{4}x\right)=\frac{8}{27}\)
\(\left(1+\frac{3}{4}x\right)=\frac{21}{8}\)
\(\frac{3}{4}x=\frac{13}{8}\)
\(x=\frac{13}{8}:\frac{3}{4}\)
\(x=\frac{13}{6}\)
Vậy \(x=\frac{13}{6}\)
\(\frac{7}{9}:\left(2+\frac{3}{4}x\right)+\frac{5}{9}=\frac{23}{27}\)
\(\frac{7}{9}:\left(2+\frac{3}{4}x\right)=\frac{23}{27}-\frac{5}{9}\)
\(2+\frac{3}{4}x=\frac{7}{9}:\frac{8}{27}=\frac{21}{8}\)
\(\frac{3}{4}x=\frac{21}{8}-2=\frac{5}{8}\)
\(x=\frac{5}{8}:\frac{3}{4}=\frac{5}{6}\)
Vậy x=5/6