In order to find the equation of the line, use the following expression for the general form of a line:
y = mx + b
where m is the slope is the line and b the y-intercept.
m is given by:
m = (y2 - y1)/(x2 - x1)
in this case (x1,y1) = (1,6) and (x2,y2) = (9,-8):
m = (- 8 - 6)/(9 - 1) = -14/8 = -7/4
next, use the following expression for a line:
y - yo = m(x - xo)
where m is the slope and (xo,yo) any point of the line. Use (xo,yo) = (1,6), and solve for y, as follow:
y - 6 = -7/4 (x - 1)
y - 6 = -7/4 x + 7/4
y = -7/4 x + 7/4 + 6
y = -7/4 x + 31/4
Hence, the required equation of the line is y = -7/4 x + 31/4