You can write two equations using the given information:
.. L = W +8
.. L * W = 609
Using substitution, you get a quadratic.
.. (W +8) * W = 609
.. W^2 +8W -609 = 0
Not surprisingly, you're looking for factors of 609 that differ by 8.
.. 609 = 1*609 = 3*203 = 7*87 = 21*29
The last two are the factors of interest.
.. (W +29)(W -21) = 0
The width of the rectangle is 21 feet, the length is 29 feet.
_____
Sometimes it is easier to work with the average dimension. Here, let that be x. Then you have
.. (x +4)(x -4) = 609
.. x^2 -16 = 609
.. x^2 = 625 = 25^2 . . . . . . . one of your memorized math facts
So, the dimensions are
.. 25 +4 = 29 by 25 -4 = 21, that is, 29 ft by 21 ft.
For this case we have the following expression:

We must evaluate the expression when:

Substituting the values we have:

Equal signs are added and the same signs are placed.

Different signs are subtracted and the sign of the major is placed:

Finally we have to:

Answer:
<span>Man, I wish I could see this answer.
Just copy you that the best answer.</span>
Hello!
We have the following expression:

Let's multiply and simplify it, look:

We multiply a*a*a, so we can rewrite it as a³. The same with b*b as b².
So, the answer in the simplified form is:
6a³ + 4b²