Notice that the two points given, share the same x-value even when the y-value changes. This is because the equation is going to be a vertical line at -4 on the x-axis. Being a vertical line, you cannot take its slope using the slope formula of: <em>m = (y2 - y1) / (x2 - x1)</em> because the denominator will result in a 0 and you cannot divide by 0 in mathematics.
