Step-by-step explanation:
we start with the point-slope form
y - y1 = a(x - x1)
where "a" is the slope, (x1, y1) is a point on the line, and then we simplify that equation giving us the slope-intercept form
y = ax + b
so,
y - -9 = -9(x - 1)
y + 9 = -9(x - 1)
and now simplifying this
y + 9 = -9x + 9
y = -9x
