Need Help with Pre Calc Functions

  • Thread starter 1busykid
  • Start date
  • Tags
    Functions
In summary, a function is a relationship between two sets, where each element in the first set is associated with exactly one element in the second set. To determine if an equation is a function, we can use the vertical line test, which states that a vertical line should only intersect the graph of a function at one point. In other words, each x-value should have only one corresponding y-value. The only exception is when the equation involves a radical, which can be a function if a restriction is placed on the domain.
  • #1
1busykid
1
0
Hey I am really confused on Functions, and my teacher does not know how to teach properly.. please help me!:cry:

I have couple of problems in book can someone explain to me how i would go about doing them...

Question: Determine whether the equation is a function?


#1: y= x²
#2: y= x³
#3: y= 1/x
#4: y= |x|
#5: y²=4-x²

Please explain to me!o:)

Reply ASAP...
 
Mathematics news on Phys.org
  • #2
This has to do with graphs right? opening up and down?
 
  • #3
A function associates exactly one value (in y) to each value in x. A vertical line through any x value should cross exactly one point.
 
  • #4
1busykid said:
Hey I am really confused on Functions, and my teacher does not know how to teach properly.. please help me!:cry:

I have couple of problems in book can someone explain to me how i would go about doing them...

Question: Determine whether the equation is a function?


#1: y= x²
#2: y= x³
#3: y= 1/x
#4: y= |x|
#5: y²=4-x²

Please explain to me!o:)

Reply ASAP...
A function f from A to B (commonly denoted as f:A→B) is a binary relation in which
[tex]\forall a \in A,\;\exists \, {!} \, f\left( a \right) \in B [/tex].

With the exception of #5,
every equation you listed is (can be represented as) a function [itex]f:\left\{ {X:x \in X} \right\} \to \left\{ {Y:y \in Y} \right\}[/itex]
 
Last edited:
  • #5
In English:

A function turns one number, usually written "x", into another number, usually written "y". For example, y = x is a function. This turns the number x into a number y -- in this case, the number y takes the same value as x. Or the function y=4x turns a number x into a number y which is four times the value of x.

The only conditions on a function is that y has to be one number. y can't be "3,4, or 5", "plus or minus 3", or so on, because those represent more than one number.

It's typical to think about functions only in terms of numbers, but a function doesn't necessarily have anything to do with numbers. Remember, although we usually have x and y stand for numbers, it can really stand for anything at all. (Why not?) x can stand for a person, or a word, or anything. For example, you can have x be a type of car, and have y equal "yes" if the car is blue and "no" if it's not. Because each type of car is either blue or not, this is an example of a function. On the other hand, if you make x be the name of a person and y be x's email address, this cannot be a function, because one person can have two email addresses.

In fancy math words, we say that the function "maps" from a certain set of things, called the domain, to another set of things, the range. The domain can be any set of things at all -- numbers, whole numbers, people, words or cars. Similarly, the range can be any set of things -- pumpkins, forums, prime numbers, dogs, etc. The only condition is that if you give it any element of the domain, the function has to pop out with only one element of the range.
 
  • #6
gnomedt said:
In fancy math words, we say that the function "maps" from a certain set of things, called the domain, to another set of things, the range.
Well, technically, a function maps from the domain to the codomain...

The range of f:A→B is simply [itex]\left\{ {f\left( a \right):a \in A} \right\} [/itex], a subset of the codomain (B).
 
Last edited:
  • #7
In even more plain English every time you see a y= and just x or stuff being done to x on the other side it is a function. If it's y^2 It's almoust never a function...unless it also has a module...

basically how to check is as it's been said above: no x-value can have 2 y values. many x-values can have same y-value. for example a vertical line is not a function but a horisontal line is.

you didn't mean "continuous" functions or "1 to 1" functions, you meant just functions right?
 
  • #8
bomba923 said:
Well, technically, a function maps from the domain to the codomain...

The range of f:A?B is simply [itex]\left\{ {f\left( a \right):a \in A} \right\} [/itex], a subset of the codomain (B).

Yes, but I didn't want to complicate it. Other people have already done that. ;)
 

FAQ: Need Help with Pre Calc Functions

What are the basic concepts of pre-calculus functions?

The basic concepts of pre-calculus functions include domain and range, graphing, transformations, inverse functions, and composition of functions.

What is the difference between a linear and non-linear function?

A linear function has a constant rate of change and can be represented by a straight line on a graph, while a non-linear function does not have a constant rate of change and cannot be represented by a straight line on a graph.

How do I find the domain and range of a function?

To find the domain of a function, you need to identify all possible x values that the function is defined for. The range of a function is all possible y values that the function can output. You can find the domain and range by analyzing the graph or by using algebraic methods.

What are the different types of functions in pre-calculus?

The different types of functions in pre-calculus include linear, quadratic, polynomial, exponential, logarithmic, and trigonometric functions.

How can I use functions in real-life situations?

Functions can be used to model and solve real-life situations such as predicting population growth, analyzing financial data, and optimizing business operations. They can also be used in engineering, physics, and other fields to describe relationships between variables.

Similar threads

Replies
12
Views
2K
Replies
2
Views
2K
Replies
2
Views
2K
Replies
1
Views
2K
Replies
1
Views
2K
Replies
11
Views
3K
Replies
1
Views
911
Back
Top