## sassyj 2 years ago Write the slope-intercept form of the equation for the line. A. y = -5/8x + 1/2 B. y = 8/5x - 1/2 C. y = 5/8x + 1/2 D. y = 8/5x + 1/2

1. sassyj

2. sassyj

3. Callisto

Where is the y-int?

4. Callisto

Note: To find y-intercept, put x =0 into the equation. When you get the y-intercept, you can eliminate one of the answers.

5. sassyj

1/2?

6. finaynay

you can determine slope using a diagram by doing rise over run (i'm not sure if you've ever heard that before) or you can do m=y2-y1/x2-x1

7. Callisto

Yes :) According to the slope-intercept form y=mx+c c is the y-intercept, m is the slope of the line. So far, which answer is wrong?

8. sassyj

B is wrong?

9. finaynay

then use point slope form y – y1 = m(x – x1) and simplify (isolate y) which will leave you with slope intercept form

10. finaynay

you can immediately get rid of A because the line isn't negative

11. Callisto

Yup! B is wrong. Next task: find the slope! To find the slope, we need two points. Can you give me two pairs of coordinates of the points lining on the line? (PS: you can refer to the figure)

12. sassyj

3,4 & 5,8?

13. Callisto

Nope :| Pair of coordinates of a point should be written like this: (x, y) Try one first, when x= 4, y=...?

14. sassyj

I am lost

15. sassyj

It must be C

16. sassyj

but unsure of the reasoning

17. Callisto

|dw:1353731289465:dw| Draw a vertical line at x=4, then it cuts at a point, find the y coordinate of that point,

18. sassyj

3

19. Callisto

Yup, so, one of the points is at (4,3) Can you pick another one now?

20. sassyj

-2,-4?

21. Callisto

Nope :| (x, y), you reversed the two :|

22. sassyj

(-4,-2)

23. sassyj

I dont know why I am not getting this. I just went back and read the entire chapter on it. It isnt sinking in at all =(

24. Callisto

(-4, -2) is right... Actually, which parts are you confusing of?

25. sassyj

I'm just not getting where the graph fits in at all

26. sassyj

I see how you are trying to break it down, but I dont see how it all connects.

27. Callisto

Sorry, I was away for a while. We know that y=mx+c is the slope intercept form, where m is the slope and c is the y-intercept. First, we find the y-intercept, which is the easiest to find. The only thing we left to do is to find the slope. To find the slope, we need two points: $$(x_1, y_1)$$ and $$(x_2, y_2)$$. Slope = m = $$\frac{y_2 - y_1}{x_2 - x_1}$$ After find the slope and the y-intercept, we plug the values of them into y=mx+c.

28. Callisto

The more general way to find the equation is $\frac{y-y_1}{x-x_1}=\frac{y_2-y_1}{x_2-x_1}$Then, isolate y to get the slope-intercept form

29. sassyj

Okay. Thank you for trying to help.