Answer :
(a) The expression that represents the side length of the coaster is, 
(b) The expression that represents the perimeter of the coaster is, 
Step-by-step explanation :
As we are given that the area of a square coaster can be represented by:

Now we are simplifying this expression by middle term splitting method.





Part (a) :
As, the area of a square is (side)², this means the side length of the square is:

Part (b) :
The perimeter of square is, 4(side)
That means,
