What is the slope of a vertical line?

The slope of a vertical line is undefined.

Explanation

Slope formula: m = (y₂ − y₁) / (x₂ − x₁)

• In a vertical line, all the x-coordinates are the same (e.g., x = 3).
• So x2 − x1 = 0.
• Division by 0 is not defined in mathematics, so the slope cannot be calculated.

Important points

• A horizontal line has slope = 0.
• A vertical line has slope = undefined.
• This distinction matters for graphing and line equations.

Final Answer: The slope of a vertical line is undefined because the change in x is zero, and division by zero is not defined.