The equation of a straight line is y = mx + c
where m = slope
and c = intercept
slope = (y2 - y1)/(x2 - x1)
y2 = 9, y1 = -1, x2 = -3, x1 =2
slope = ( 9- (- 1)) /(-3-(+2))
slope =10/(-3-2)
slope = 10/-5
slope = -2
puting the slope in the equation we have y = -2x + c
Using any 2 points given say (2, -1)
where x = 2 and y = -1
we can find c by substitution
-1 = (-2 x 2) + c
c = -1 +4
c = 3
the equation is y = -2x + 3