Question

A rectangle has perimeter 40 cm.
Let the length of one side be x. Then write a function A(x) that represents that area of the rectangle

Answer 1

if you call the other side \(w\) then \(2w+2x=40\) and \[A=wx\] solve the first equation for \(w\) and get
\[2w+2x=40\\
2w=40-2x\\
w=20-x\] then substitute back in to \[A=wx\] and get
\[A(x)=(20-x)x\] or if you prefer
\[A(x)=20x-x^2\]

Answer 2

Do you know how I would graph this on a graphing calculator by chance?