Limits: What is the limit of ((2+h)^4 - 16)/h as h approaches 0?

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Homework Help Overview

The discussion revolves around evaluating the limit of the expression ((2+h)^4 - 16)/h as h approaches 0, which falls under the topic of limits in calculus.

Discussion Character

  • Exploratory, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss various methods for simplifying the expression, including factoring and expanding polynomials. There are attempts to manipulate the numerator to facilitate taking the limit.

Discussion Status

Some participants have provided guidance on expanding and simplifying the expression, while others are exploring different approaches. There is a sense of progress as one participant indicates they have arrived at an answer, but no consensus on the method's ease has been established.

Contextual Notes

One participant mentions the answer in the textbook, which raises questions about the correctness of their methods and whether there is a simpler approach to the problem.

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Homework Statement


Evaluate
lim ((2+h)^4 - 16)/h
h->0



Homework Equations


Difference of squares


The Attempt at a Solution


knowing that the top of the fraction is a difference of squares
i factored it and arrived at lim h->0 ((2+h)^2+4)((2+h)^2-4)/h
this is where i got stuck
 
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Try multiplying the numerator expression to simplify instead of factoring it.
 
Now just expand both [itex](2+h)^{2}[/itex] as well, and then distribute what's left in the numerator. If you completely simplify the whole thing to expand that giant polynomial at the top, you might be able to cancel that h in the denominator and take the limit.
 
well, i think i followed your method quark which was to expand the (2+h)^2
i ended up (after simplification) with lim h->0 (h^2 + 4h + 8)(h^2 + 4h)/h but i do not know how to expand that. can you please show me how to arrive to the answer?

the answer in the back of the textbook is 32.

also, is this the easiest way to solve the problem?
 
From:
[tex]\frac{(h^{2}+4h+8)(h^{2}+4h)}{h}[/tex]
You can distribute the numerator. It works the same way as if you were going to distribute/foil something like (a+b)(c+d)=(ac+da+bc+dc)

In this case it would be something more like this:
(a+b+c)(d+e+f) = (ad+ae+af+bd+be+bf+cd+ce+cf)

I think the easiest way of solving this problem (without using any calculus other than the limit) would be to expand the ()^4 right from the start. It's important to know how to distribute like shown above though.
 
QuarkCharmer said:
From:
[tex]\frac{(h^{2}+4h+8)(h^{2}+4h)}{h}[/tex]
You can distribute the numerator. It works the same way as if you were going to distribute/foil something like (a+b)(c+d)=(ac+da+bc+dc)

In this case it would be something more like this:
(a+b+c)(d+e+f) = (ad+ae+af+bd+be+bf+cd+ce+cf)

I think the easiest way of solving this problem (without using any calculus other than the limit) would be to expand the ()^4 right from the start. It's important to know how to distribute like shown above though.

alright, I've arrived at my answer :)
thank you very much
 

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