Question

a rectangular field is to be enclosed by a fence. an existing fence will form one side of the enclosure. the amount of new fence bought for the other 3 sides is 1200ft. what is the maximum area of the enclosed field?

Answer 1

@lgbasallote

Answer 2

the existing fence length was not given/

Answer 3

?

Answer 4

i have this much

Answer 5

nope :\

Answer 6

i smell calculus... @hartnn take over please

Answer 7

yea its precalc lol

Answer 8

u have 2x+y= 1200
and you need to maximize area xy , right ?

Answer 9

umm...i need to the know the max area of the field

Answer 10

can u take derivatives ?

Answer 11

the answer is apparently 180,000ft^2 but idk how to get that

Answer 12

i dont know what those are lol sorry

Answer 13

if you are not taught derivatives, then this is not calculus!
which specific topic does this question belong ?

Answer 14

idk its basic functions and stuff

Answer 15

its not calc its precalc

Answer 16

ok, let me try
2x+y=1200

f(x) = x (1200-2x)
= -2x^2 +1200 x
now this is quadratic function

Answer 17

compare it with f(x)=ax^2+bx+c
then the maximum value of x occurs at -b/2a

Answer 18

wha... L(*.*L)

Answer 19

so here it will occur at x=1200/4 = 300
now find y= 1200-2(300)
then find area =xy = ......

Answer 20

which actually comes out to be 180000 ft^2

Answer 21

its not supposed to be this complicated....idk what she (the teacher) wants me to do with this question....i see youre getting the right answer but surely this isnt the way im supposed to get it

Answer 22

lol! u want complicated way ? use derivatives... this is the easiest i can think of......

Answer 23

one sec ill try graphing

Answer 24

it gives me x=600 which would make the area 360,000 :S

Answer 25

u graphed -2x^2 +1200 x right ?

Answer 26

i dont understand how you made it into a quadratic, could u explain that?

Answer 27

2x+y=1200 , u got right ?

Answer 28

howd you make 2x+y=1200 into that?

Answer 29

yea

Answer 30

so y=-2x+1200

Answer 31

howd u get the square?

Answer 32

AREA = length * breadth = x*y
put that y in this

Answer 33

Vertex of parabola, right?

Answer 34

so wait we're comparing 2x+y=1200 and 2x*2y=A
A-1200=y
(2x*2y)-(2x+y)=y
2x2y-2x+y=y
k now i just confused myself lol

Answer 35

y=-2x+1200
f(x) = xy = x(-2x+1200) = ??

Answer 36

2x+y=1200
y=1200-2x
area = xy = 1200x-2x^2

Answer 37

ooohh...okay so x*y=x(1200-2x)=-2x^2+1200x
k ill graph that

Answer 38

and yes, find vertex of that parabola

Answer 39

x=-1200/-4
x=300
so that means y=600
and that gives 180,000

YAY T(^_^T)

Answer 40

u got it :)

Answer 41

thanks so much hartnn :)

Answer 42

welcome ^_^

Answer 43

^_^