How do I estimate the value of a limit and determine if it exists using a graph?

In summary: So in this case, f(x) does not exist at 2, and does exist at 2.5 and 4. In summary, the limit of f(x) as x-> c exists if as x gets arbitrarily close to c then f(x) gets arbitrarily close to some unique value.
  • #1
sugarcoatit
1
0
So we are learning about limits right now and I can't do my homework because I don't understand. Is there anyone who can explain to me how you do things such as estimate the value of ..., explain why a quantity does or does not exist and how you go about using a graph to get all your answers.

Thanks,

sugarcoatit
 
Physics news on Phys.org
  • #2
I need more information to help you out. What specific problem are you having problems understanding? If you need a general explanation/definition of a limit, I suggest looking at your textbook, on Wikipedia, or asking a teacher.
 
  • #3
To estimate the value of a limit, let’s say lim f(x) as x->c you guess what f(x) gets really really close too as x gets closer to c. For example let’s say we want to estimate the limit of f(x) = (x^2-1)/(x-1) as x->1. Let’s first notice that f(x) is actually undefined at 1, since the denominator would be 0. But we can still talk about what happens as we get close, so let’s pick some trial numbers that progressively get closer to 1. how about 2,1.5,1.1, 1.01, and 1.0001.

So
f(2) = 3
f(1.5) = 2.5
f(1.1) = 2.1
f(1.01) = 2.01
f(1.0001) = 2.0001

It seems as x gets closer to 1, f(x) gets closer to 2. If we do the same thing from the other side (x values less than 1) it will get close to 2 also. So a good estimation of our limit would be 2. But notice this is by no means an exact or even good process, soon you will learn a formal way to tell exactly what limits are equal too.

For your next question. When does a limit exist? Since I don’t think you have the formal definition of a limit yet I’ll give you an intuitive one. The limit of f(x) as x-> c exist if as x gets arbitrarily close to c then f(x) gets arbitrarily close to some unique value. So let’s take f(x) = 1/x as x-> 0. This limit doesn’t exist because f(x) at 0 doesn’t get close to a value let alone a unique value. In this case we say f(x) diverges at c. Let’s consider another case f(x) = x+1 if x =< 2, x^2 if x > 2. Lim f(x) as x->2 doesn’t exist. Because x+1 gets close to 3, and x^2 gets close to 4. So as x gets close to 2, f(x) doesn’t approach a single value, it approaches 2.
 

FAQ: How do I estimate the value of a limit and determine if it exists using a graph?

What is a limit?

A limit is a fundamental concept in calculus that describes the behavior of a function as the input approaches a specific value. It tells us the value that a function is approaching, rather than the actual value at that point.

How do you find the limit of a function?

To find the limit of a function, you can use algebraic manipulation, graphing, or mathematical rules such as L'Hôpital's rule. You can also use a table of values to estimate the limit. However, the most accurate way to find a limit is using the formal definition, which involves evaluating the function at values that are closer and closer to the desired input value.

What is a derivative?

A derivative is a mathematical concept that represents the instantaneous rate of change of a function at a specific point. It is the slope of the tangent line to the graph of the function at that point.

How do you find the derivative of a function?

To find the derivative of a function, you can use the power rule, product rule, quotient rule, or chain rule. You can also use the definition of a derivative, which involves taking the limit of the difference quotient as the change in input approaches zero.

What is the relationship between limits and derivatives?

Limits and derivatives are closely related in calculus. The derivative of a function at a specific point is the limit of the difference quotient as the change in input approaches zero. In other words, the derivative is a special type of limit. The concept of a limit is essential for understanding and calculating derivatives.

Similar threads

Replies
9
Views
488
Replies
2
Views
3K
Replies
26
Views
2K
Replies
53
Views
2K
Replies
6
Views
1K
Back
Top