A)\(\frac{x+1}{4}-\frac{x+2}{5}+\frac{x+4}{7}-\frac{x+5}{8}+\frac{x+7}{10}-\frac{x+9}{12}=0\)
B)\(\frac{x}{2004}+\frac{x+1}{2005}+\frac{x+2}{2006}+\frac{x+3}{2006}=4\)
C)\(\frac{x+2}{x-3}+\frac{x-2}{x+3}-\frac{2\left(x^2+6\right)}{x^2-9}=0\)
D)\(\frac{x^2-15x+1}{x+17}=x-2\)
E)\(\frac{x}{x^2+5x+6}=\frac{2}{x^2+3x+1}\)
a) \(\frac{x+1}{4}-\frac{x+2}{5}+\frac{x+4}{7}-\frac{x+5}{8}+\frac{x+7}{10}-\frac{x+9}{12}=0\)
\(\Leftrightarrow\left(\frac{x+4-3}{4}+\frac{x+7-3}{7}+\frac{x+10-3}{10}\right)-\left(\frac{x+5-3}{5}+\frac{x+8-3}{8}+\frac{x+12-3}{12}\right)=0\)
\(\Leftrightarrow\left(x-3\right)\left(\frac{1}{4}+\frac{1}{7}+\frac{1}{10}\right)-\left(x-3\right)\left(\frac{1}{3}+\frac{1}{8}+\frac{1}{12}\right)=0\)
\(\Leftrightarrow\left(x-3\right)\left(\frac{1}{4}-\frac{1}{5}+\frac{1}{7}-\frac{1}{8}+\frac{1}{10}-\frac{1}{12}\right)=0\)
\(\Leftrightarrow x=3\)
Vậy x=3
d) \(\frac{x^2-15x+1}{x+17}=x-2\Leftrightarrow x^2-15x+1=x^2+15x-34\)
\(\Leftrightarrow30x=35\Leftrightarrow x=\frac{7}{6}\)
vậy x=7/6