Question

which graph has a slope of zero? red blue neither

Explanation:

Step1: Recall slope definition

Slope formula: $m=\frac{y_2 - y_1}{x_2 - x_1}$. For slope 0, $y_2 - y_1 = 0$ (horizontal line).

Step2: Analyze graphs

• Red line: Vertical ($x = 3$), $x$ changes, $y$ varies. Slope undefined (division by 0).
• Blue line: Horizontal ($y = -1$), $y$ constant. So $y_2 - y_1 = 0$, slope $m = 0$.

Answer:

Blue