SAT and ACT math terms · SAT Math, ACT Math
Vertex form
Vertex form: The form f(x) = a(x − h)² + k of a quadratic, which shows the vertex (h, k) directly.
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What it means
In vertex form, h and k give the coordinates of the maximum or minimum point. To convert from standard form, complete the square or use x = −b/(2a) to find h and substitute to find k.
Watch the sign: f(x) = (x + 3)² − 5 has vertex (−3, −5).
Example
A ball's height is h(t) = −16(t − 2)² + 70. The maximum height is 70 feet at t = 2 seconds.
On the exam
Questions ask for maximum or minimum values in context or which equivalent form shows the vertex.