Part A:

The first step of completing the square is writing the expression 

 as 

 which expands to 

.
We have the first two terms exactly the same with the function we start with: 

 and 

 but we need to add/subtract from the last term, 49, to obtain 41. 
So the second step is to subtract -8 from the expression 

The function in completing the square form is

Part B:
The vertex is obtained by equating the expression in the bracket from part A to zero


It means the curve has a turning point at x = -7
This vertex is a minimum since the function will make a U-shape. 
A quadratic function 

 can either make U-shape or ∩-shape depends on the value of the constant 

 that goes with 

. When 

 is (+), the curve is U-shape. When 

 (-), the curve is ∩-shape
Part C:
The symmetry line of the curve will pass through the vertex, hence the symmetry line is 

This function is shown in the diagram below