## anonymous one year ago quick question.... On a xy-coordinate how do i know what to plug in the y2-y1/x2-x1 formula

1. idku

u should know the 2 points through which your line is going or one x or y coordinate can be not given, but then you have to know the slope to solve for this coordinate

2. anonymous

if the y-intercept is 12 and the x-intercept is 5 ... how do i know which one to plug in where?

3. Nnesha

y = mx + b where m is slope and b is y-intercept x-intercept is when y =0 so you can write it in parentheses (x,y)----->>(5,0)

4. anonymous

no but in the y2-y1/x2/x1

5. Nnesha

ohh so if y-intercept is 12 remember y-intercept when line cross y-axis when x=0 so (0 ,12) and x-intercept like i say x when line cross x-axis when y = 0 so (5,0)

6. anonymous

yea so how do i know which goes first in the y2-y1/x2-x1

7. Nnesha

|dw:1433802336037:dw| and it doesn't matter just remember y values should be at the top

8. anonymous

so it doesn't mater if the 12 is y2 or y1 in the equation? and the same for the 5 ?

9. Nnesha

yes right :-)

10. anonymous

oh.... hmmmmm well lemme try my question because i got something different...

11. anonymous

wait no it's not it....

12. anonymous

i'm supposed to get a -12/5 but if i plug it in anywhere i can also get a positive 12/5

13. Nnesha

or you can see which number is coming first for exxample (5,0)(0,12)|dw:1433802577923:dw| (0,12) is first so y_1 is 12 that's how i do it

14. anonymous

so left to right whatever is first? so it would be 12-0/ 0-5?

15. Nnesha

it doesn't matter you will get the same answer :-)

16. anonymous

ohhh okay so always right to left?

17. Nnesha

yep that works too

18. Nnesha

$$\color{blue}{\text{Originally Posted by}}$$ @yomamabf i'm supposed to get a -12/5 but if i plug it in anywhere i can also get a positive 12/5 $$\color{blue}{\text{End of Quote}}$$ (5,0)(0,12) $\huge\rm \frac{ 12-0 }{ 0-5 }=-\frac{ 12 }{ 5 }$ now other way (0,12)(5,0) $\frac{ 0-12 }{ 5-0} = \frac{ -12 }{ 5 }$ same ?

19. anonymous

oh okay i got it

20. Nnesha

u will get the same answer :-)

21. anonymous

also it can be this too right? y=m(5)+12 =-12/5

22. Nnesha

nope x_2 - x_1 = 5 in this case bec x = 0 so that will work but NO!

23. Nnesha

Let x_2 = 3 and x_1 = 1 x_2 - x_1 = 2-1 =1 so you CAN'T substitute 1 for just x

24. anonymous

hmmm okay

25. Nnesha

yeah :-)

26. anonymous

thank you <333

27. Nnesha

but you can pick any x value from two order pair (5,0)(0,12) to plug in this equation y = mx+b u will get the same answer

28. Nnesha

my pleasure :-) gO_Od luck!