2.10.2a 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) $f(x)=2x^2-6x+7$
(c) $f(x)=5-2x-x^2$
(d) $f(x)=4+12x-3x^2$