A line passes through (1,7) and has slope 0. Which equation is correct?

• A. y = x + 6
• B. y = x - 1
• C. y = 7
• D. y = -x + 7

Answer: (C)

A line with slope 0 is horizontal, meaning its y-value stays the same for all x. Since the line passes through the point with y-coordinate 7, every point on the line has y = 7. So the equation is y = 7, a horizontal line at height 7.

Other options describe lines that aren’t horizontal (they have nonzero slope). They either change y as x changes, or, if you plug the given x-value, don’t give y = 7. For example, lines with positive or negative slope rise or fall as x changes, so they can’t match a horizontal line through (1, 7).