Answer:
d. 9x + 63 and 63 square feet
Step-by-step explanation:
Given
Original
[tex]Length = x[/tex]
[tex]Width = 9[/tex]
Extended
[tex]Length = x + 7[/tex]
[tex]Width = 9[/tex]
[tex]Area = 9(x + 7)[/tex]
Required
Determine an expression and the value of the extended area
First, we calculate the area of the original desk
[tex]A_1 = x * 9[/tex]
[tex]A_1 = 9x[/tex]
From the given parameters, we have:
[tex]Area = 9(x + 7)[/tex] --- area of the new surface
Open bracket
[tex]Area = 9x + 63[/tex]
The area of the new surface is the summation of the area of the original desk and the area of the extended portion (E)
So:
[tex]Area = A_1 + E[/tex]
Make E the subject
[tex]E= Area - A_1[/tex]
[tex]E= 9x + 63 - 9x[/tex]
[tex]E= 63[/tex]
Hence, the area of the extended portion is 63