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**Mathando****Member**- Registered: 2018-06-20
- Posts: 3

Could someone help explain the expansion below:

Square(x+Δx) -> square(x)+ 2x Δx + square(Δx)

In my understanding, below should be the correct expansion:

Square(x+Δx) -> square(x) + square(Δx)

My question is from reading “introduction to derivative” article on MathIsFun

Thanks,

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**ganesh****Administrator**- Registered: 2005-06-28
- Posts: 26,286

Hi Mathando,

The slope formula is:

Put in and .

Simplify and cancel

Simplify more (divide through by Δx): = 2x + Δx

Then as Δx heads towards 0 we get: = 2x

It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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**Mathando****Member**- Registered: 2018-06-20
- Posts: 3

http://www.mathisfunforum.com/latex/b/1/4e18c1f224b02b22693d61ffad4eff1.gif

Could you elaborate about more. Where does 2x delta x come from ?

Thanks

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**ganesh****Administrator**- Registered: 2005-06-28
- Posts: 26,286

Hi,

.

It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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**Mathando****Member**- Registered: 2018-06-20
- Posts: 3

Thanks

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