No one in the group plays better than Nam

chx làm đc câu b :>

\(\dfrac{a+2x}{a-2}-\dfrac{a-2x}{a+2}=\dfrac{6a}{a^2-4}\)

a) Khi a = 3 ta có :

\(3+2x-\dfrac{3-2x}{5}=\dfrac{18}{5}\\ \Leftrightarrow3+2x=\dfrac{18}{5}+\dfrac{3-2x}{5}\\ \Leftrightarrow3+2x=\dfrac{21-2x}{5}\\ \Leftrightarrow15+10x=21-2x\\ \Leftrightarrow12x=6\\ \Leftrightarrow x=\dfrac{1}{2}\)

b. ĐK :\(x\ne-1\\;x\ne0\)

\(\dfrac{x+3}{x+1}-\dfrac{3x^2+4x+1}{x\left(x+1\right)}=\dfrac{x-1}{x}\\ \Leftrightarrow\dfrac{x^2+3x-3x^2-4x-1}{x\left(x+1\right)}=\dfrac{\left(x-1\right)\left(x+1\right)}{x\left(x+1\right)}\\ -2x^2-x-1=x^2-1\\ \Leftrightarrow3x^2+x=0\\ x\left(3x+1\right)=0\\ \Leftrightarrow\left\{{}\begin{matrix}x=0\left(KTM\right)\\x=-\dfrac{1}{3}\left(TM\right)\end{matrix}\right.\) 

\(\Rightarrow x=-\dfrac{1}{3}\)