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

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

anonymous · Answer

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 
$$A(x)=20x-x^2$$

anonymous · Answer

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