In the vertex (h, k) of a parabola, what does k represent?

• A. The vertical coordinate of the vertex
• B. The horizontal coordinate of the vertex
• C. The slope at the vertex
• D. The leading coefficient

Answer: (A)

The vertex is written as (h, k), where h tells how far left or right the vertex sits and k tells how high or low it sits. So k is the vertical coordinate, the y-value of the vertex. In the standard vertex form y = a(x − h)² + k, the k term shifts the graph up or down by k units, placing the vertex at the point (h, k). The horizontal position comes from h, and the leading coefficient a affects width and direction, not the vertex’s position. For example, if the vertex is (3, 4), the vertex lies at y = 4, with x = 3.