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## nagdy1 3 years ago Write an equation in point-slope form of the line through point J(4, 1) with slope –4.

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1. AriPotta

do you know what point-slope form is?

2. nagdy1

yes

3. AriPotta

so this should be easy. just substitute the numbers in

4. nagdy1

how

5. nagdy1

give u hard time

6. nagdy1

sorry

7. nagdy1

:(

8. AriPotta

tell me what point-slope form is.

9. nagdy1

tells a difference between two points on a line.

10. AriPotta

what?

11. nagdy1

The point-slope form expresses the fact that the difference in the y coordinate between two points on a line (that is, y − y1) is proportional to the difference in the x coordinate (that is, x − x1). The proportionality constant is m (the slope of the line).

12. AriPotta

it's y - y1 = m(x - x1) idk if that's what you meant...

13. AriPotta

brb i gotta walk mah dog

14. nagdy1

at night

15. nagdy1

im at USA

16. AriPotta

alright i'm back

17. AriPotta

so it should be easy. you're just substituting the y in the coordinate for y1, the x in the coordinate for x1, and -4 for m

18. nagdy1

so the answer is y - y1 = m(x - x1)

19. AriPotta

no, you didn't substitute

20. AriPotta

our point is (4,1) so x1 is 4 and y1 is 1

21. nagdy1

y - y1 = m(x - x1) y – 1 = (-4)(x – 4) y - 1 = -4(x - 4) y - 1 = -4x + 16 y = -4x + 16 + 1 y = -4x + 17

22. AriPotta

which one is it then?

23. nagdy1

y = -4x + 17

24. nagdy1

STEp by STEp y - y1 = m(x - x1) y – 1 = (-4)(x – 4) y - 1 = -4(x - 4) y - 1 = -4x + 16 y = -4x + 16 + 1 y = -4x + 17

25. AriPotta

i thought the answer was supposed to be in point-slope form

26. nagdy1

so how can i write y = -4x + 17 to point-slope form

27. AriPotta

lol. it was already in point-slope in step 1. y - 1 = -4(x - 4)

28. nagdy1

haha never knew that

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