In this example 41.. it said, root 5 is maximum or minimum. Then, what did we do after we get 3>root5 ?!..

41. Find the maximum and minimum values, if any , of the following function given by. 

$$\begin{gathered} \left(i\right) f\left(x\right) = (2x-1{)}^2+3 (ii) f(x) =9x^2+12x +2 \\ (iii) f(x) = -(x-1{)}^2+10 \left(iv\right) f\left(x\right) =x^2+1 \end{gathered}$$