Answer:
Undefined
Explanation:
Looking at the change in x's theres no variation which means this is a vertical line, thus therefore this is an undefined line as the rise over the run or the change in y over the change in x will result in a divide by 0 situation making it (-4, all real numbers) aka undefined.
slope = rise/run = change in y/change in x = (y2-y1)/(x2-x1)
Hope this helps :)