Find the equation that describes a line which passes through (9, - 13) and is perpendicular to a line with an undefined slope. Express in both slope-intercept form and standard form (if possible).

• A. y = 13, y = 13
• B. x = 9, x = 9
• C. y = - 13, y = - 13
• D. x = - 9, x = - 9

Answer: (C)