## 85295james 3 years ago Write a rule for the linear function in the graph.

1. 85295james

the lines are (4,3) (3,-1)

2. 85295james

A. y =-4 x + 13 B. y = -4x – 13 C. y =4 x – 13

3. theEric

Do you know the general "point-slope" formula?\[y=mx+b\] Are you familiar with that?

4. 85295james

no

5. theEric

Alright, well this formula is how you define a line! For a line, the "m" and "b" variables will be numbers instead. "m" is "slope" and "b" is "y-intercept" Are either of those familiar to you? And are you familiar with plotting points on a graph using a formula?

6. 85295james

|dw:1346091835332:dw|

7. theEric

I can immediately answer your problem, but I want to work it throug with you.

8. theEric

And I agree with your plot! :)

9. 85295james

yes i would like that

10. eliassaab

You do not really need to do all this for a multiple choice question.

11. eliassaab

Just replace in the 3 equations and see which one works

12. eliassaab

13. theEric

eliassaab is correct. eliassaab recommends that you take the x value of one point and put it into the equation, you should get the y value of that point from calculating the correct option.

14. theEric

There's another quick method to determine if a formua might be right, just by looking to see if "m" and "b" are positive on your plot and then finding the choice that has those same positive or negatives. That requires a little knowledge of how it works anyway. Wold you like to work through this as if there are no multiple choices?

15. theEric

That would be helpful for both finding the answer without choices, and understanding the concept some more in a different way than the substitution method of eliassaab.

16. 85295james

thank you

17. theEric

Would you like to work through it as if there were no multiple choice, then? :) eliassaab's method will work every time for multiple choice, though.

18. theEric

By looking at a picture with no points, you can narrow down the possible equations. By going through some algebra, you can find the equation by knowing any two points on the line.

19. 85295james

no thank you but i need more help with other questions

20. theEric

Alright. I'll look for them on here! :)

21. theEric

And C is the answer, as eliassaab said :)

22. 85295james

thanks =)

23. theEric

No problem!!