Persamaan garis lurus yang melalui titik (2,-1) dan(5,8) mempunyai gradien...

Y2 - y1
----------
X2 - x1

8 - (-1)
--------
5 - 2

8 + 1
-------
3

9
-- = 3
3

Jawabannya 3

(2,-1)
x1=2
y1=-1

(5,8)
x2=5
y2=8

[tex] \frac{y - y1}{y2 - y1} = \frac{x - x1}{x2 - x1} \\ \frac{ y + 1 }{8 + 1} = \frac{x - 2}{5 - 2} \\ \frac{y + 1}{9} = \frac{x - 2}{3} \\ kalikan \: silang \\ 3(y + 1) = 9(x - 2) \\ [/tex]
3y+1 = 9x-2
3y-9x=-1-2
3y-9x=-3

a=-9
b=3

m=a/b
m=-9/3
m=-3