Expert: Ahmed Salami - 6/9/2010

Question
width of a rectangle: 2x - 5 ft.
length of a rectangle: 3x + 9ft.
Write a polynomial P(x) that represents the  perimeter and the evaluate if x is 4ft.

Answer
Hi Sharon,
The perimeter P of a rectangle with length l and width w is the distance around it i.e
P = 2l + 2w
 = 2(l + w)
Now,
l = 3x + 9
w = 2x - 5
Then,
P(x) = 2[(3x + 9) + (2x - 5)]
    = 2[3x + 9 + 2x - 5]
    = 2(5x + 4)
    = 10x + 8
When x = 4 ft
P(4) = 10(4) + 8
    = 40 + 8
    = 48 ft

Regards