Double check

Jubbly · #1 $Old$ December 3rd, 2008, 05:16 PM

I just need a double check with my problems about point slope the one with the forumula like y-y1=m(x-x1)

(6,-4), (3,5) answer y=1x+8
(2,7), (1,-4) answer y=11x-43
(-5,13), (-10,9) I got -4/5x+1

If I got all three of these correct then I know what I'm doing If I don't I might come back to ask for more help...

Thanks for helping me!

nzmathman · #2 $Old$ December 4th, 2008, 05:36 PM

For coordinates: (6, -4) and (3, 5)

$gradient (m) = \frac{-4-5}{6-3} = \frac{-9}{3} = -3$

Substituting:

$y - 5 = -3 (x - 3)$

$y = -3x + 14$

For coordinates: (2, 7) and (1, -4)

$gradient (m) = \frac{7 - -4}{2-1} = \frac{11}{1} = 11$

Substituting:

$y - 7 = 11 (x - 2)$

$y = 11x - 15$

For coordinates: (-5, 13) and (-10, 9)

$gradient (m) = \frac{13 - 9}{-5 - -10} = \frac{4}{5}$

Substituting:

$y - 13 = \frac{4}{5} (x + 5)$

$y = \frac{4}{5} x +17$