Drexel dragonThe Math ForumDonate to the Math Forum

Ask Dr. Math - Questions and Answers from our Archives
Associated Topics || Dr. Math Home || Search Dr. Math

Factoring to Find the Limit

Date: 11/5/95 at 23:2:15
From: John Florance
Subject: limits...

Hi Doc...
lim         x   +   8
x -> -2    -----------      =       ???
            x   +   2

i.e., how to factor the numerator?


Date: 11/6/95 at 11:7:0
From: Doctor Ethan
Subject: Re: limits...

Hey John,

Here is the deal.

We have to factor the top into two factors so that we can cancel with 
the bottom.  Fortunately there is a standard rule for factoring things
that are in the form of a^3 + b^3

If I tell you the first factor do you think you can figure out the 

The first looks like a + b  or in the case of this problem x + 2.  
So what would the second factor have to be in order to work out?

I will tell you that it is a trinomial of highest power two.

So you need to figure out: 

(x + 2)(what goes here) = (x^3 + 8)

Have fun.  I think that you can figure it out.

If you can't, write back and we will help you.

-Doctor Ethan,  The Geometry Forum

Associated Topics:
High School Basic Algebra

Search the Dr. Math Library:

Find items containing (put spaces between keywords):
Click only once for faster results:

[ Choose "whole words" when searching for a word like age.]

all keywords, in any order at least one, that exact phrase
parts of words whole words

Submit your own question to Dr. Math

[Privacy Policy] [Terms of Use]

Math Forum Home || Math Library || Quick Reference || Math Forum Search

Ask Dr. MathTM
© 1994-2015 The Math Forum