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#1 2010-06-18 11:02:05

lakeheadca
Member
Registered: 2010-01-31
Posts: 37

Create an equation

A rectangle or square with perimeter 100cm, area 25 cm² what will be the equation.
is it
w²+25w+100
w²+50w+25
w²+25w-100
the third option i dont remember.
Please explaine
thank you.

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Last edited by lakeheadca (2010-06-18 11:04:26)

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#2 2010-06-18 11:20:05

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 88,791

Re: Create an equation

Hi;

Start by using the equations for A and P.

P = 100 = 2L + 2W

A = 25 = L * W

Solving from the first equation:

L = 100 - 2W = 50 - W

Can you finish from here?


In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

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#3 2010-06-19 03:58:52

lakeheadca
Member
Registered: 2010-01-31
Posts: 37

Re: Create an equation

Please can you explain that actually what this question is asking.  What this equation will do. I still don't know how to come up the equation. Am I finding length which is equal to this function. It is quadratic equation, so there are two W??
I am not good in math. Sorry.

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#4 2010-06-19 05:22:19

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 88,791

Re: Create an equation

Hi lakeheadca;

We have the 2 equations:

P = 100 = 2L + 2W

A = 25 = L * W     These are easy. But not easy to solve for all those variables. So we try to eliminate one. We solve for the L from the first equation.

L = 100 - 2W = 50 - W

25 = L * W   Substitute 50 - W for L

25 = ( 50 - W ) W  This is a quadratic, so expand it.

25 = 50W - W^2 

W^2 - 50 W + 25 = 0

Now solve by the quadratic formula. Are you Okay with this? Or do you need more help? After you get the answer I will go over the equations with you.


In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

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