Help on part a please
I found the second derivative as being y=-2 so how do I substitute my value of x=2 to find if it's a min or max?

Max

Step-by-step explanation:

y" = -2

Basically is a constant value of -2, which doesn't depend on x.

Find the turning point using y' = 0.

y' = 4 - 2x = 0

4 - 2x = 0

x = 2

So the turning point is at x = 2,

y = 5 + 4(2) - 2² = 9

(2,9) is the turning point

For the nature (max/min):

y" = -2

Since y" < 0, it is a maximum turning point