Answer:
a. P = 6x + 8
b. P = 44
Explanation:
The formula for the perimeter of a rectangle/envelope is the sum of all the sides which would be the following
P = length + length + width + width
Based on the description we can say that the length is equal to the following arithmetic expression
L = 2x + 4
a. Therefore, now we can plug this value into the Perimeter formula to create a polynomial for it
P = (2x + 4) + (2x + 4) + x + x
P = 6x + 8
b. To find the perimeter of an envelope with a width of 6 we simply need to substitute 6 for x and solve for P using the Polynomial above.
P = 6(6) + 8
P = 36 + 8
P = 44