Answer:
y = 4
Step-by-step explanation:
It doesn't exactly have a real equivalent as in y = mx + b.
It's actual equation is y = 4. All x values are permitted. y = 4 is a function: it passes the vertical line test. (Any x has only 1 y value associated with it).
The equation I gave you is really y = 0*x + b which reduces down to y = b or y = 4.
