2,
\(\dfrac{x}{x-2}+\dfrac{3}{x+2}=\dfrac{x^2+3x-6}{x^2-4}\)
\(\Leftrightarrow x\left(x+2\right)+3\left(x-2\right)=x^2+3x-6\)
\(\Leftrightarrow x^2+2x+3x-6=x^2+3x-6\)
\(\Leftrightarrow2x=0\)
\(\Leftrightarrow x=0\)
3,
\(a,5x-3=2x+6\)
\(\Leftrightarrow3x=9\)
\(\Leftrightarrow x=3\)
\(b,\dfrac{5x}{4}+\dfrac{x-2}{3}\ge\dfrac{17x}{12}\)
\(\Leftrightarrow15x+4\left(x-2\right)\ge17x\)
\(\Leftrightarrow15x+4x-8\ge17x\)
\(\Leftrightarrow2x\ge8\)
\(\Leftrightarrow x\ge4\)