Resol els límits

1. \( \displaystyle \lim_{x \to  \infty} \dfrac {x^2+x+4}{2-4x} \)
   
   
2. \(\displaystyle \lim_{x \to  -\infty} \dfrac {x^2+x+4}{2-4x} \)
   
   
3. \(\displaystyle \lim_{x \to  1} \dfrac {x^2-x}{2-2x} \)
   
   
4. \(\displaystyle \lim_{x \to  1} \dfrac {x^2+x}{x-1} \)
   
   
5. \(\displaystyle \lim_{x \to  1} \dfrac {-3}{x^2-2x+1} \)
   
   
6. \(\displaystyle \lim_{x \to  -\infty} \dfrac {-3}{x^2-2x+1} \)
   
   
7. \(\displaystyle \lim_{x \to  -1} \dfrac {x-1}{2x+2} \)
   
   
8. \(\displaystyle \lim_{x \to  \infty} \dfrac {x-1}{2x+2} \)
   
   
9. \(\displaystyle \lim_{x \to  -\infty} \dfrac {x-1}{2x+2} \)
   
   
10. \(\displaystyle \lim_{x \to  \infty } 2^{x+3} \)
    
    
11. \(\displaystyle \lim_{x \to  \infty } \log_2 (1-x^2) \)
    
    
12. \(\displaystyle \lim_{x \to  -\infty } e^{\frac 1 x} \)