Can someone please help i need to write the equation of the green line

f(x) = ax + b

(0, -4):

           f(0) = a•0 + b

           f(0) = b      ⇒     b = -4

(12, 0):

           0 = a•12 + b

           0 = 12a - 4

           4 = 12a

The equation of the green line:

or:      

step-by-step explanation:

0

x = 3 ± √(5+y)