Need help

Finding trigonometric expression

sec (arctan x/2) 

Hello  Lolaaaaaa!

$f(x)=sec (arctan\ \frac{x}{2})=\frac{1}{cos\ (arctan\ \frac{x}{2})}$

   x :  1        2        3          4        5         6         7         10 

f(x) : 1.118 1.414  1.803  2.236  2.693  3.162  3.640  5.100 

  !

What are the coordinates of the hole in the function?

f(x)=2x2−5x−123x2−11x−4

Is anyone able to help me with this? Would greatly appreciate it!