Which of the following limits are correct?
- $\displaystyle \lim_{x\rightarrow 0} \frac{x^2+2x}{2x}=1$
- $\displaystyle \lim_{x\rightarrow 1/2 }\frac{2x^2+x-1}{2x-1}=\frac{3}{2}$
- $\displaystyle \lim_{x\rightarrow \infty } 18x^3 – 12x^2 +1=\infty$
- $\displaystyle \lim_{x\rightarrow -\infty} 8x^3 – 12x^2 +1=-\infty$