Writing linear equations

Writing linear equations

Reminders

We have learned about two relationships that are represented by the following equations:

 $y=x+b$  
 $y=mx$  

Multiple Choice

What is the correct equation for an additive relationship?

• y = x + b

• x = y + b

• y = mx

• y/x = m

Multiple Choice

What is the correct equation for a multiplicative relationship?

• y = x + b

• x = y + b

• y = mx

• y/x = m

 $y=x+b$  

• This equation will represent situations where something is being added to or subtracted from the x-value. 

• Look out for words in word problems like: more than, less than

 $y=mx$  

• This equation will represent situations where the x-value is being multiplied or divided. 

• Look out for words in word problems like: each, per

Let's practice

I do

• We will write the equation in the form of y = mx or y = x + b for the situation.

• Samantha had to pay $4 more than Joe had to pay for a video game.

• I spy the key words: "more than"

• It seems to be an addition

• My answer is:  $y=x+4$  

I do again

• We will write the equation in the form of y = mx or y = x + b for the situation.

• Oranges at the super market cost $0.89 each.

• I spy the key words: "each"

• It seems to be a multiplication

• My answer is:  $y=0.89x$  

Now it's your turn

Write the equation in the form of y = mx or y = x + b for each situation.