\(\lim\limits_{x\rightarrow0}\frac{\left(2x+1\right)^{\frac{1}{2}}-\left(3x+1\right)^{\frac{1}{3}}}{x^2}=\lim\limits_{x\rightarrow0}\frac{\left(2x+1\right)^{-\frac{1}{2}}-\left(3x+1\right)^{-\frac{2}{3}}}{2x}\)
\(=\lim\limits_{x\rightarrow0}\frac{-\left(2x+1\right)^{-\frac{3}{2}}+2\left(3x+1\right)^{-\frac{5}{3}}}{2}=\frac{-1+2}{2}=\frac{1}{2}\)