Arectangular deck has a area of 320 ft squared. the length of the desk is 4 feet longer than the width. find the dimensions of the desk. solve by completing the square.

Because l•w= area, area= 320, l=w+4
width • (width +4)= 320

Distribute the multiplication over addition and move all to the left side.
w^2 +4w-320=0
(w-16)•(w+20)=0 yet, The product of two things is 0 if one is 0 or both are 0 so
w-16=0 so w=16 and
w+20=0 so w= -20

Now the width or length could not be negative so we discard the solution w=-20.

Answer
width= 16 inches
length =16+4=20

Verify
w•l=320
16•20=320✔️