## Nick88888888 one year ago Find the equation in slope-intercept form of the line through points (-2, 5) and (6, -15). How would i do this? Do i use y = mx+b? or what im not sure how to do it

1. 16shuston

ya use y=mx+b

2. 16shuston

do you know how to figure out the slope?

3. Nick88888888

No ;-;

4. 16shuston

okay so it will be change in y over change in x

5. Nick88888888

I mean i was asking cause i was trying to search how to do it and some would say y = mx+b and then some would be solving it like this (-2,5) and (6, -15) First find slope. (m) (y2-y1)/(x2-x1) m=(-15-5)/(6-2)

6. 16shuston

ya you are doing it right so far

7. 16shuston

so then when you find m you use a set o your points to find b.

8. 16shuston

do you want me to show you?

9. anonymous

10. Nick88888888

wait so like this? (-2,5) and (6, -15) First find slope. (m) (y2-y1)/(x2-x1) m=(-15-5)/(6-2) m=-20/4 is the slope now replace x and y terms (y = mx+b) 5=-20/4*2+b? is that correct so far?

11. triciaal

x2 -x1 = 6 - (-2) so it becomes 6 + 2

12. Nick88888888

oh.. so (-2,5) and (6, -15) First find slope. (m) (y2-y1)/(x2-x1) x2 -x1 = 6 - (-2) so it becomes 6 + 2 m=(-15-5)/(6+2) m=-20/8 is the slope now replace x and y terms (y = mx+b) 5=-20/8*2+b?

13. triciaal

so the slope is -20/8 = -5/2 using one of the given points, (x1, y1) and (x,y) y-y1 = -5/2(x-x1)

14. Nick88888888

This is how a certain site said to do it :/ (-2,5) and (6, -15) First find slope. (m) (y2-y1)/(x2-x1) x2 -x1 = 6 - (-2) so it becomes 6 + 2 m=(-15-5)/(6+2) m=-20/8 is the slope now replace x and y terms (y = mx+b) 5=-20/8*2+b? 5=-40/8+b 5+40/8=b (40+40)/8=b 80/8=b the y intercept Thus equation being y=-20x/8+80/8

15. triciaal

@Nick88888888 you don't need a site to tell you to always reduce to the lowest term

16. butterflydreamer

hmm... not quite. First you want to find the slope (m) So, use the formula: |dw:1435467038575:dw| Then you want to use the formula: y = mx + b (this is your point-intercept formula) Use (-2, 5) where (x,y) therefore x = -3, y = 5 and we know m(slope) = -20/8 Therefore: $y=mx + b \rightarrow 5= -20/8 \times-2 +b$ From here, multiply everything by 8 to get rid of the fraction: 5*8 = -20(-2) + 8b 40 = 40 + 8b Subtract 40 from both sides, 40 - 40 = 40 + 8b - 40 0 = 8b Find the value of b by dividing both sides by 8 and we get b = 0 Then plug this into your formula: y= mx + b , where we now know the value of m and b :)

17. UsukiDoll

k the m is -20/8 so we just need the other formula $y-y_{1}=\frac{-5}{2}(x-x_1)$

18. UsukiDoll

y_1 = 5 x_1 = -2

19. triciaal

@Nick from your post above "now replace x and y terms (y = mx+b) 5=-20/8*2+b?" the process is correct but you made a mistake x is -2 you used 2

20. UsukiDoll

you need to distribute the negative because x_1 = -2 $y-5=\frac{-5}{2}(x+2))$

21. UsukiDoll

I got -5/2 because -20/8 can be reduced further... divide both of them by 4

22. UsukiDoll

then you have to distribute that -5/2 to x and -5/2 to 2 afterwards add 5 to both sides.