ACT Preparation / Unit 11 ACT 1014 short lesson, about 20 seconds
Axis of Symmetry
Captions available
The idea
A parabola is symmetric about the vertical line through its vertex, x = −b/(2a); the vertex is (−b/(2a), f(−b/(2a))).
In practice
f(x) = x² − 6x + 5: x = 6/2 = 3, and f(3) = −4, so the vertex is (3, −4).
Where people slip
The zeros sit at equal distances on either side of the axis: here, 1 and 5.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
Builds on
Unlocks
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