A rectangle has width of 4 feet. Find a function that models it's area A in terms of Its perimeter P.

Question

campbell_st · Answer

Start with what you know about the perimeter

P = 2(4) + 2l

or

P = 2l + 8


so make l the subject. 

now for Area 

Area = l * w

you know w = 4 

so using what you know 

Area = 4l

now substitute the value of l from the perimeter

for the final answer

anonymous · Answer

Where do I plug that in ?

campbell_st · Answer

$$Area =4 \times l$$

and the perimeter is 

$$P = 8 + 2l$$

can you make l the subject... in the perimeter equation

anonymous · Answer

The answer is suppose to be A(P) = 2P-16 ??

campbell_st · Answer

yep... we'll get to that... 

in the perimeter equation above can you make length (l) the subject...