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## #1 2018-06-20 15:36:35

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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## #2 2018-06-20 21:16:18

ganesh
Registered: 2005-06-28
Posts: 26,844

Hi Mathando,

Introduction to Derivative.

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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## #3 2018-06-21 07:27:45

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

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

Thanks

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## #4 2018-06-21 14:59:34

ganesh
Registered: 2005-06-28
Posts: 26,844

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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## #5 2018-06-21 23:53:53

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