Using Limit Laws to Solve for f(x)

In summary: It is indeterminate. We cannot determine the value of the limit without further information about the function f(x).
  • #1
jmm12
4
0

Homework Statement


lim ( f(x)/(x2) )= 8
x→0

Then what is...

a)lim ( f(x) )
x→0

b)lim ( f(x)/x )
x→0




Homework Equations





The Attempt at a Solution



tried separating the limits
(lim x→0 f(x))(lim x→0 1/(x2)) = 8

but the lim x→0 1/(x2) is ∞ ... soooo i don't know...
 
Last edited:
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  • #2
welcome to pf!

hi jmm12! welcome to pf! :wink:

tell us what you think (and why), and then we'll comment! :smile:
 
  • #3


tiny-tim said:
hi jmm12! welcome to pf! :wink:

tell us what you think (and why), and then we'll comment! :smile:

its in my post now, please help
 
  • #4
The only thing in your post is
tried separating the limits
(lim x→0 f(x))(lim x→0 1/(x^2)) = 8
and that is NOT in general true. Since the denominator goes to 0, what must the numerator go to in order that this limit exist?
 
  • #5
draw the graph of 1/x2 (near zero) …

roughly what do you think the graph of f(x) will have to look like if f(x)/x2 -> 8 ? :wink:
 
  • #6
so if the numerator has to be zero too..
then the lim x->0 f(x) is zero?
 
  • #7
that's correct! :smile:

but now prove it ! :biggrin:
 
  • #8
what would lim f(x) / x as x->0 be then..

if (lim x->0 f(x)) / (lim x->0 x)

0/0...or dne?
 

FAQ: Using Limit Laws to Solve for f(x)

How do I use limit laws to find the value of f(x)?

The first step in using limit laws to find the value of f(x) is to identify which limit law is applicable to the given function. Once you have determined the correct limit law, you can apply it to the function and evaluate the limit using algebraic manipulation and substitution.

What are the different types of limit laws?

There are several types of limit laws, including the sum law, difference law, product law, quotient law, and power law. Each of these laws has a specific purpose and can be used to simplify the evaluation of limits.

Can I use limit laws for all types of functions?

No, limit laws can only be applied to functions that are continuous at the point where the limit is being evaluated. If the function is not continuous, other methods, such as L'Hospital's rule, may need to be used to find the limit.

When should I use the squeeze theorem instead of limit laws?

The squeeze theorem should be used when the limit of a function cannot be evaluated directly using limit laws. This may occur when the function is undefined at the point where the limit is being evaluated, or when the function is oscillating or discontinuous at that point.

Are there any limitations to using limit laws?

Yes, there are some limitations to using limit laws. For example, limit laws cannot be used to evaluate limits at points where the function is undefined or at points of discontinuity. Additionally, some functions may require more advanced techniques, such as Taylor series, to find the limit.

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