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### Course: 8th grade > Unit 3

Lesson 13: Linear and nonlinear functions- Recognizing linear functions
- Linear & nonlinear functions: table
- Linear & nonlinear functions: word problem
- Linear & nonlinear functions: missing value
- Linear & nonlinear functions
- Interpreting a graph example
- Interpreting graphs of functions
- Linear equations and functions: FAQ

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# Linear equations and functions: FAQ

Frequently asked questions about linear equations and functions

## What is a proportional relationship?

A proportional relationship is when two quantities change so that they maintain a constant ratio to one another. For example, if $y$ is directly proportional to $x$ , then if $x$ doubles, $y$ will also double. And if $x$ triples, $y$ will also triple, and so on.

## What do we mean by "solutions" to linear equations?

Solutions to linear equations are the $x$ and $y$ values that make the equation true. For example, $(2,7)$ is a solution to the equation $y=3x+1$ because when we substitute $2$ in for $x$ and $7$ in for $y$ , we get a true statement: $7=3(2)+1$ .

## What is slope?

Slope is a measure of the steepness of a line. It is calculated by dividing the rise (change in $y$ ) by the run (change in $x$ ) between two points on the line.

## What are intercepts?

Intercepts are the points at which a line crosses the $x$ - or $y$ -axis. The $x$ -intercept is the point at which the line crosses the $x$ -axis, and the $y$ -intercept is the point at which the line crosses the $y$ -axis.

## What is slope-intercept form?

Slope-intercept form is a way of writing a linear equation. It has the form $y=mx+b$ , where $m$ is the slope and $b$ is the $y$ -intercept.

## How do we graph a line in slope-intercept form?

To graph a line in slope-intercept form, we can start by plotting the $y$ -intercept, which is given by the $b$ value in the equation. From there, we can use the slope (the $m$ value) to find more points on the line.

## How do we write an equation in slope-intercept form?

To write an equation in slope-intercept form, we need to find the slope and the $y$ -intercept of the line. We can use two points on the line to calculate the slope, and we can use the slope and one of the points to solve for the $y$ -intercept.

## What is a function?

A function is a mathematical rule that matches inputs to outputs. We can think of it like a machine: put a number in, the machine does some calculations, and out pops a corresponding number.

Inputs and outputs don't have to be numbers. Functions themselves can be inputs and outputs.

## What is a linear function?

A linear function is a type of function that produces a straight line when graphed. It follows the form $y=mx+b$ , where $m$ is the slope and $b$ is the $y$ -intercept.

## How do we compare two linear functions?

We can compare two linear functions by looking at their slopes and $y$ -intercepts. If the slopes are the same, the lines are parallel. If the slopes are different, the lines will intersect at some point. We can also compare the $y$ -intercepts to determine where the lines cross the $y$ -axis.

## How do we construct a linear model for a real-world relationship?

To construct a linear model, we need to determine the slope and $y$ -intercept of the relationship. We can use two data points to find the slope, and then use one of the data points to solve for the $y$ -intercept.

## What are some real-world applications of linear functions?

Linear functions can be used to model many real-world relationships. For example, a company might use a linear function to predict future sales based on past performance. A scientist might use a linear function to model the relationship between two variables in an experiment. Linear functions can also be used in finance to calculate interest rates or investment returns.

## Want to join the conversation?

- If i have 12w x 27

and "w" is a whopper from burger king, what would be the answer?(7 votes)- Well, assuming that the 27 is 27 cents, the answer would be:

12 Whoppers x 27 cents, meaning that you could buy 12 whoppers for 27 cents. I hope you enjoyed my very mathematical answer :D(6 votes)

- Is there a way to remember a formula other than writing it down(2 votes)
- Scientists have not yet determined how
*remembering something*works, i. e. the process of retrieving information from your brain.

Writing down a formula is a step that happens*after*you have successfully remembered it, but how do you remember something in first place, we don’t know.

It is therefore difficult to suggest you any way for better remembering something. A good start would be*to learn*intensely.

Learning something well is groundwork for remembering it later.*Poor learning*usually correlates to reduced probability in successfully remembering it.(4 votes)

- Help I understand nothing(2 votes)
- If you feel like you don't understand something, you can always review the things you learned in the past.(3 votes)

- How does the proportional relationship double, triple, etc?(1 vote)
- So let's say we have 2 variables x and y that are directly proportional to each other.

x ∝ y

We can write an equation to display this relationship.

x = k * y, where k is a constant.

So now we double x. For the R.H.S. to equal this, and since k is a constant, y is doubled as well.

2x = k * (2y)

How about we triple y instead. For L.H.S. to equal this, x has to be tripled as well.

3x = k * (3y)

Notice no matter how many times any of the variable is multiplied, the ratio maintains the same.

Initially:

x : (k * y)

Doubled:

2x : (k * 2y)

x : (k * y)

Tripled

3x : (k * 3y)

x : (k * y)(3 votes)

- What is the meaning of linear functions and nonlinear functions(1 vote)
- how do we graph a word problem equation?(0 votes)
- It depends on the word problem.

But you should identity the independent variable and the dependent variable.

The dependent variable is the variable that is being studied or observed to determine how it changes in response to the manipulation of other variables. It is the outcome or result of the experiment or study, so it is usually y in the linear equation.

On the other hand, the independent variable might be something that constantly changes, such as time. It is usually x in the linear equation.(2 votes)

- why do I have to do math when I have the internet and a calculator(0 votes)
- Because then you wouldn’t have an intuitive sense of mathematics; if you typed 10*10 instead of 10*11 on your calculator by mistake and the answer was 100, you would get the wrong answer and you wouldn’t even know it.(4 votes)

- Why does linear functions help us a lot and could you live if you don't know it?(0 votes)
- unless you're a scientist, most of this stuff doesn't help in your everyday life.(1 vote)

- if hot dogs are $1 why does he need to sell 20 hot dogs to get an extra $12 he should make $20. that makes no since(0 votes)
- Because he also needs to make up for the $8 he spent on hot dog supplies. Until he makes the $8, he's not making a profit.(1 vote)