## anonymous one year ago MEDAL + FAN !!!!!!!!!!!!!!!!!!!!!!!!!

• This Question is Open
1. anonymous

2. anonymous

@igreen

3. anonymous

@mathstudent55

4. anonymous

@mathmate

5. anonymous

@is3535

6. anonymous

...

7. mathstudent55

Do you know the slope-intercept form of the equation of a line? \(y = mx + b\)

8. anonymous

yes i recognize that

9. mathstudent55

That is above the figure you provided. The b part is where the line crosses the y-axis. That is called the y-intercept. Look in the given graph. At what point on the y-axis does the line cross the y-axis?

10. anonymous

110

11. mathstudent55

Great. We no have that b = 110, and we have this much: \(y = mx + 110\) Now we need to find m, the slope.

12. anonymous

ok

13. mathstudent55

To find the slope, you can use two points of the line. Pick two points that are easy to read on your graph. That means, pick two points that are on intersections of the grid lines. Can you read two points?

14. anonymous

yes i can

15. mathstudent55

One point can be the one that includes y = 110.

16. anonymous

(10,110) ?

17. mathstudent55

Close. It's (0, 110). Since it's on the y-axis, the x-coordinate is 0. (0, 110) is a good point. Now we need another one.

18. anonymous

see i was going to say 0 but i thought it wouldn't count since 0 is the orgin

19. anonymous

but it makes since since (0,110) = 110

20. anonymous

my next one is (10,90)

21. anonymous

also i just realized that 10,110 is not on the line anyway , lal

22. mathstudent55

You get to the point we are talking about, (0, 110), by starting at the origin. You go 0 right or left. That is why the x-coordinate is 0. Then you go 110 up. That makes the y-coordinate 110. The point is (0, 110) That means start at the origin, go 0 right or left (you're still at the origin), then go up 110. You end up at the point 110 on the y-axis.

23. anonymous

exactly ^

24. mathstudent55

Yes, (10, 90) is a good point because it's easy to read since it falls on the grid lines. Another easy point would be (20, 70). Ok, let's use (0, 110) and (10, 90)

25. anonymous

ok now whet?

26. mathstudent55

We need to find the slope of the line that has those two points. The way to find the slope is subtract the two y-coordinates. Then subtract the two x-coordinates. Divide the first difference by the second difference.

27. anonymous

like x^1 - x^2 y^1 - y^2

28. mathstudent55

|dw:1434398858240:dw|

29. anonymous

oops i was backwords

30. mathstudent55

The order does not matter, as long as you do both subtractions int he same order.

31. mathstudent55

|dw:1434399014025:dw|

32. anonymous

-20/10 is what i got

33. mathstudent55

Now we need to do the subtractions in the numerator and denominator.

34. anonymous

|dw:1434399153286:dw|

35. anonymous

|dw:1434399177385:dw|

36. anonymous

|dw:1434399221808:dw|

37. anonymous

am i correct? @mathstudent55

38. mathstudent55

|dw:1434399234449:dw|

39. anonymous

:D

40. mathstudent55

You have a fraction. A fraction means division.

41. anonymous

i know but i thought you said subtract

42. mathstudent55

|dw:1434399290651:dw|

43. anonymous

|dw:1434399386993:dw|

44. mathstudent55

You subtract the y's and you subtract the x's. Then you divide one subtraction by the other one.

45. mathstudent55

Yes. The slope is -2. That goes in the m of the slope-intercept equation.

46. anonymous

y=-2x+110 :D

47. mathstudent55

Correct.

48. mathstudent55

Notice that if we used the points in the other order, the slope would still be the same:

49. mathstudent55

|dw:1434399447815:dw|

50. anonymous

OK i would just like to say thank you very much for your time here, you have helped me far beyond me expectations, there for, i shall fan you in hope that i may be able to ask for your assistance again c;

51. mathstudent55

When you use two points to find the slope, it makes no difference which point you use first and which point you use second for the y- and x-coordinate subtractions. The important thing is to do both subtractions in the same order.

52. anonymous

I have another problem like this and i will message you if i need help on it, thank you and good day sir

53. mathstudent55

You are very welcome. Thanks for paying attention. You did a great job! Feel free to ask me for help anytime. It's just that now I gtg.