Just to be different we'll start with intercept intercept form which says the line through x intercept (a,0) and y intercept (0,b) is
Through (4,0) and (0,-2) that's
Multiply through by the common denominator of 4 for standard form:
x - 2y = 4
For slope intercept form we solve for y
-2 y = -x + 4
y = (1/2) x - 2
We see our slope is (1/2) and we go through (4,0) so point slope form is
y - 0 = (1/2)(x - 4)
y = (1/2)(x-4)