The lengths of the sides are 20 cm and 20 cm
Step-by-step explanation:
Given
Perimeter, P = 80cm
Represent the length and width with L and W, respectively;
Substitute 80 for P
Divide through by 2
Make L the subject of formula
Area of a rectangle is calculated as thus;
Substitute 40 - B for L
Express this as a function
Set A(B) = 0 to determine the roots
Hence;
or
or
or
The maximum area of a rectangle occurs at half the sum of the roots;
So;
Recall that
Hence the lengths of the sides are 20 cm and 20 cm