Question

How do I find the length?
A rectangle is drawn so that the width is 2 feet shorter than the length. The area of the rectangle is 63 square feet. Find the length of the rectangle.

Answer 1

we can calculus the area of rectangle by formula: width*length = area
call: w is width and l is length so we have: area = w*l
and width is 2 feet shorter than the length so: w = l - 2.
sub it to function we have: area = (l-2)*l = 63
so: l^2 - 2l - 63 = 0. From now can you solve for solution?

Answer 2

@hosiduy so I do 1-21-63?

Answer 3

Oh no, those are not 1's, they are L's. :D
\[L^2-2L-63=0\]

Answer 4

@agentc0re oops lol I still don't get how do I solve that?

Answer 5

Quadratic Equation. :D

Answer 6

So I would add 2L to the other side? @agentc0re

Answer 7

Oh no no no. The quadratic equation is this:
\[\huge x={-b \pm \sqrt{b^2 - 4*a*c} \over 2a}\]

Answer 8

have you seen that before?

Answer 9

no ;(

Answer 10

HELPPPP

Answer 11

@agentc0re

Answer 12

well that equation is used when you have an equation in the form:
\[\huge ax^2+bx+c\]

In this case, you have L instead of x.
Make sense?

Answer 13

a, b and c are the numbers or coefficients in front of the x's, or L's in your case.

Answer 14

So it's L^2+2L+63 ? @agentc0re

Answer 15

it is but knowing what i said from above, what is a, b and c?

Answer 16

Idk Did I do it in the right order? @agentc0re

Answer 17

I'll give yo a hint... b=2, try to figure out a and c.

Answer 18

c=63

Answer 19

IDK what I am doing!

Answer 20

@agentc0re

Answer 21

Yup, so b=2, c=63, what about a? I know, thats why i am trying to walk you through this.

Answer 22

2L !

Answer 23

So it's 2L+2+63?

Answer 24

no

Answer 25

:(

Answer 26

what number is in front of
\[\huge L^2\]

Answer 27

What did I do wrong?

Answer 28

2L^2+2L+63

Answer 29

\[\huge L^2+2L+63 =0\] is your answer but you have to solve for L.
In order to solve for L you have to use the quadratic equation, which is what i'm trying to teach to you but you're not figuring out how to get a, b and c which is what we need to plug it in to the formula i gave you to get our solution for L. :D

It's quite possible that you're solution doesn't need to be L but it's just the polynomial.

Answer 30

I'm so lost so to find the length of the triangle I have to plug those #'s into the equation...

Answer 31

This should help. http://www.youtube.com/watch?v=EeVqtpuMFOU

Answer 32

@agentc0re

Answer 33

Ok I plugged in the numbers like the guy did in the video but I got -248 you can't sqrt that?!

Answer 34

Nope, unfortunately you can't. :/ Well you can, but you're going to have part of an answer that is imaginary.

Answer 35

Good job tho, that's really impressive to have watched that video and then used the quadratic formula. :D

Answer 36

@agentc0re So how do I find the length of my triangle?

Answer 37

triangle?? you mean rectangle...
why don't you try factoring first..... that would've been faster....:)

Answer 38

hey desibaybee, did u get this!

Answer 39

NO :( @cfraser007

Answer 40

Do you have the answers to this problem? Or is it something you have to enter in online?

Answer 41

ok...I am trying! lets c how far i get, b4 i start helping u!

Answer 42

@agentc0re No thats exactly how it is and I have to fill in the blank!

Answer 43

Then the answer you got by using the quadratic equation is correct. Even though it's not a real length, it is the correct answer unless there's been a typo of the problem along the way. There is no way to factor this so that it's solvable (at least I don't see it)

Answer 44

I don't think you are suppose to use that formula for this because I didn't learn that in class? @agentc0re

Answer 45

What level of Math class is this?

Answer 46

what did u learn...or what methods? or what was the lesson you all were talking about before seeing this problem!

Answer 47

algebra but like development 2

Answer 48

factoring stuff like that but I remember him just making an equation out of it

Answer 49

haha! this problem is so simple guys! v r bunch of too smart folks trying to overthink it! lol...ok solution here it is! area of a rectangle is 63...and the width is 2 feet shorter than the length! so...the difference between 2 numbers must b 2 and multiply to equal 63! the only set is 7 and 9! since 7 x 9 = 63 and 9 - 7 = 2! I think, now u can figure out which one is width and which one is length!
Enjoy!

Answer 50

@cfraser007 yeah when I factored it I got 7 and 9 but witch is the length and which is the width?

Answer 51

So is the width 7?

Answer 52

yes!!

Answer 53

@Desibaybee we had a sign messed up. the equation needed to be: \[\huge x^2-2x-63\]
solve that using the equation now, you'll see that you get those answers.

Answer 54

@cfraser007 WOOOOO THANK YOU SOOO MUCH OMGSHHH THAT TOOK ME FOREVER SO SIMPLE!!! ALL WE HAD TO DO WAS FACTOR THE EQUATION!!! :D

Answer 55

i'm sorry i didn't catch the sign error before. :/

Answer 56

@agentc0re It's ok hun thanks so much for trying and helping tho! :)

Answer 57

NO NO NO, this is not factoring!!! i promise you this is not factoring.

Answer 58

Well when I factored it and put 9 for the length it was right! @agentc0re

Answer 59

factoring is when you have\[\huge x^2+2x+1 = (x+1)(x+1)\]
Foiling, is when you do the reverse. I'm just trying to help with the terminology. Anyways, glad you got the answer. :D

Answer 60

agentcOre, I see where u r getting at! u get (L+7)(L-9) = 0, then L= -7 and L= 9! May b u r concerned about the negative signs! but it should not b a problem...just say that, v take absolute values since v r dealing with lengths and distances... ! problem solved! (i think!)

Answer 61

oh! my bad! agentcOre!

Answer 62

@cfraser007 Ya, that is factoring but i didn't see that being done until just now. There was a math error on my part when trying to explain the quadratic formula and i dropped a minus sign when i shouldn't have. I think we're all confused. hahahhaha. OH well.

Answer 63

haha! lol