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

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.

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

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 102,410

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.****If it ain't broke, fix it until it is.** **A number by itself is useful, but it is far more useful to know how accurate or certain that number is.**

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

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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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 102,410

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.****If it ain't broke, fix it until it is.** **A number by itself is useful, but it is far more useful to know how accurate or certain that number is.**

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