First let us find the slope of the line using the two points (3,1), (2,9) given.
x1 = 3, y1 = 1, x2 = 2, y2 =9
m = (y2 - y1)/(x2 - x1).
m = (9 - 1)/(2 - 3).
m = 8/-1 = - 8.
Therefore slope, m = -8.
Using y = mx + c. Slope = m, m = -8.
y = -8x + c
Substituting any of the point (3,1) into the equation, x = 3, y = 1.
1 = -8(3) + c
1 = -24 + c
1+24 = c
25 = c
c = 25 Substituting into y = mx + c, m =-8, c = 25
Therefore y = -8x + 25.
y = -8x + 25.
That's it . Cheers.