Question

A rectangular field is to be enclosed on four sides with a fence. Fencing cost $5/ft on two sides. Other sides cost $8/ft. Find the dim of the field
with an A=830ft^2 that is the cheapest to enclose?

Answer 1

dim = dimension ?

Answer 2

yes

Answer 3

l=830/w thats about as far as ive gotten

Answer 4

w=28.8?

Answer 5

we need to find the prime factors of 830 in order to find combination of 2 min possible multiples of 830 because then only we will find cheapest endorsement
we can do it like this
let's take length=l and width =w so
830=l*w
as u said
l=830/w
now cost of fencing=8*w +5*l
put l=830/w here
so cost=8*w+(5*830)/w
now differntiate it with respect to w
and since we want to minimize it
equate this expression to 0