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15 tháng 1 2019

\(-\frac{21}{13x}+\frac{1}{3}=-\frac{2}{3}\)

\(\frac{-21}{13x}=\frac{-2}{3}-\frac{1}{3}\)

\(\frac{-21}{13x}=\frac{-3}{3}\)

\(\frac{-21}{13x}=\frac{-21}{21}\)

=> 13x = 21

 x = 21 : 13

x = 21/13

15 tháng 1 2019

\(\Rightarrow\)\(\frac{-21}{13x}=\)\(\frac{-2}{3}-\frac{1}{3}=-1\)\(\Rightarrow\frac{21}{13x}=1\)\(\Rightarrow13x=21\Rightarrow x=\frac{21}{13}\)

Vậy x=\(\frac{21}{13}\)

a, \(\frac{8x-3}{4}-\frac{3x-2}{2}=\frac{2x-1}{2}+\frac{x+3}{4}\)

\(\frac{8x-3}{4}-\frac{6x-4}{4}=\frac{4x-2}{4}+\frac{x+3}{4}\)

\(8x-3-6x-4=4x-2+x+2\)

\(2x-7=5x\Leftrightarrow2x-5x+7=0\Leftrightarrow-3x=-7\Leftrightarrow x=\frac{7}{3}\)

b, \(\frac{x+3}{2}-\frac{x-1}{3}=\frac{x+5}{6}+1\)

\(\frac{3x+9}{6}-\frac{2x-2}{6}=\frac{x+5}{6}+\frac{6}{6}\)

\(3x+9-2x-2=x+5+6\)

\(x+7=x+11\Leftrightarrow-4\ne0\)

27 tháng 4 2020

thanks

30 tháng 1 2017

\(P=\frac{\left(\frac{2x-3}{4x^2-12x+5}+\frac{2x-8}{13x-2x^2-20}-\frac{3}{2x-1}\right)}{\left(\frac{21+2x-8x^2}{4x^2+4x-3}\right)}+1\)

\(=\frac{\left(\frac{2x-3}{4x^2-2x-10x+5}+\frac{-2\left(4-x\right)}{8x-2x^2+5x-20}-\frac{3}{2x-1}\right)}{\left(\frac{21-12x+14x-8x^2}{4x^2+6x-2x-3}\right)}+1\)

\(=\frac{\left(\frac{2x-3}{2x\left(2x-1\right)-5\left(2x-1\right)}+\frac{-2\left(4-x\right)}{2x\left(4-x\right)-5\left(4-x\right)}-\frac{3}{2x-1}\right)}{\left(\frac{3\left(7-4x\right)+2x\left(7-4x\right)}{2x\left(2x+3\right)-\left(2x+3\right)}\right)}+1\)

\(=\frac{\left(\frac{2x-3}{\left(2x-1\right)\left(2x-5\right)}+\frac{-2\left(4-x\right)}{\left(2x-5\right)\left(4-x\right)}-\frac{3}{2x-1}\right)}{\frac{\left(7-4x\right)\left(3+2x\right)}{\left(2x+3\right)\left(2x-1\right)}}+1\)

\(=\frac{\left(\frac{2x-3}{\left(2x-1\right)\left(2x-5\right)}+\frac{-2\left(2x-1\right)}{\left(2x-1\right)\left(2x-5\right)}-\frac{3\left(2x-5\right)}{\left(2x-1\right)\left(2x-5\right)}\right)}{\frac{7-4x}{2x-1}}+1\)

\(=\frac{2x-3-4x+2-6x+15}{\left(2x-1\right)\left(2x-5\right)}\times\frac{2x-1}{7-4x}+1\)

\(=\frac{14-8x}{2x-5}\times\frac{1}{7-4x}+1\)

\(=\frac{2\left(7-4x\right)}{2x-5}\times\frac{1}{7-4x}+\frac{2x-5}{2x-5}\)

\(=\frac{2+2x-5}{2x-5}\)

\(=\frac{2x-3}{2x-5}\)

27 tháng 6 2019

TL:

a)

\(\frac{14\left(x-3\right)}{21}+\frac{7\left(x-5\right)}{21}=\frac{13x+4}{21}\) 

\(\frac{14x-42+7x-35}{21}=\frac{13x+4}{21}\) 

21x-77=13x+4

21x-13x=77+4

8x=81

x=\(\frac{81}{8}\) 

2 câu còn lại bn lm cách tương tự 

hc tốt