diketahui persamaan garis y = mx+c. tentukan nilai m dan c jika garis tersebut melalui titik: a. (2,1) dan (-3, -1) b. (2,0) dan (0,4) c. (-4,2) dan ( 3,-3) tol

Bab Persamaan Garis
Matematika SMP Kelas VIII

a] (2, 1) dan (-3, -1)

    (y - y1) / (y2 - y1) = (x - x1) / (x2 - x1)
    (y - 1) / (-1 - 1) = (x - 2) / (-3 - 2)
    (y - 1) / (-2) = (x - 2) / (-5)
    y - 1 = (-2) . (x - 2) / (-5)
    y = (2x - 4)/5 + 1
    y = (2x - 4 + 5)/5
    y = (2x + 1)/5
    y = (2/5) x + (1/5)

    m = 2/5
    c = 1/5

b] (2, 0) dan (0, 4)
 
    (y - y1) / (y2 - y1) = (x - x1) / (x2 - x1)
    (y - 0) / (4 - 0) = (x - 2) / (0 - 2)
    y = 4 (x -2) / -2
    y = -2 (x - 2)
    y = -2x + 4

    m = -2
    c = 4

c] (-4, 2) dan (3, -3)

    (y - y1) / (y2 - y1) = (x - x1) / (x2 - x1)
    (y - 2) / (-3 - 2) = (x - (-4)) / (3 - (-4))
    y - 2 = (-5) (x + 4) / 7
    y = (-5x - 20)/7 + 2
    y = (-5x - 20 + 14)/7
    y = (-5x - 6)/7
    y = (-5/7) x - (6/7)

    m = -5/7
     c = -6/7