Proving the Limit of a Complicated Function using Variables and Compositions

In summary, the conversation is about a complicated limits problem involving variables and functions. The problem is to prove the limit of h°g°f(x) as x approaches a is equal to d. The conversation includes a step-by-step explanation of how to solve the problem by substituting variables and applying the limit laws. The conversation also includes a final confirmation that the solution is correct.
  • #1
Hygelac
13
0
I'm stuck on one complicated limits problem, wondering if any of you could help me :) usually I am pretty fine with limits but this one uses all variables and has functions in it. Anyways, here it is:

f(a) = b, g(b) = c, h(c) = d
prove lim[x->a](h°g°f)(a) = d

(° = "of")

Can anyone help me?
 
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  • #2
lim[x->a](h(g(f(x)))) = d eh?

Well as x->a, f(x)->b
let y = f(x)
So now we have lim[y->b](h(g(y)))

as y->b, g(y)->c

Make sense? I guess the rest is obvious
 
  • #3
Thanks for your help, I just thought of something else, too. Seems like this works and is very easy, could you do just a quick check of it and see if it makes sense?

f(a) = b, g(b) = c, h(c) = d

lim[x->a](h(g(f(a)))) = d

f(a) = b, so g(f(a)) = g(b)
g(b) = c, so h(g(b)) = h(c)
h(c) = d, which solves the problem
 
  • #4
Looks good to me. You may want to play it safe I'm not sure how meticulous your teacher expects you to me but I would accept that answer :)
 
  • #5
Thanks a bunch :)
 

1. What is a limit problem?

A limit problem is a mathematical concept that involves determining the value a function approaches as its input approaches a specific value, typically referred to as the limit point. It is often used in calculus to analyze the behavior of functions near certain points.

2. What are the different types of limit problems?

The two main types of limit problems are one-sided limits and two-sided limits. One-sided limits involve approaching the limit point from only one direction, while two-sided limits involve approaching the limit point from both directions.

3. How do you solve a limit problem?

To solve a limit problem, you can use algebraic manipulation, substitution, or graphical analysis. Additionally, you can use the rules of limits, such as the sum, difference, product, and quotient rules, to simplify the expression and evaluate the limit.

4. What are some common techniques for evaluating limits?

Some common techniques for evaluating limits include factoring, rationalizing the numerator or denominator, using trigonometric identities, and applying L'Hopital's rule. These techniques can help simplify the expression and make it easier to evaluate the limit.

5. Why are limit problems important?

Limit problems are important because they allow us to understand the behavior of functions and the relationship between their inputs and outputs. They are also essential in calculus and other fields of mathematics, as they provide the foundation for concepts such as continuity and differentiability.

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