Example 1 : Finding the Maximum and Minimum points of Quadratic Function using completing the square

Example 1 

Find the maximum or minimum value of each of the following quadratic function by completing the squares.  In each case, state the value of x at which the function is maximum or minimum.  And also, state the maximum or minimum point and axis of symmetry for each case.

(a) f(x)= x 2 +6x+7
(b) f(x)=2 x 2 6x+7
(c) f(x)=52x x 2
(d) f(x)=4+12x3 x 2