The slope intercept form of (-4, 8) and (9, 8)

Step 1: Find the slope

(y-y) / (x-x) = (8-8) / (9+4) = 0

Step 2: Substitute into the slope intercept equation

y - y = m (x - x)

y - 8 = 0 (x - 9)

If the problem just wants plain, slope intercept form, then this is your answer.

If not, y = 8