The axis of symmetry of a parabola is a line about which the parabola is symmetrical.

When the parabola is vertical, the line of symmetry is vertical.

When a quadratic function is graphed in the coordinate plane, the resulting parabola and corresponding axis of symmetry are vertical.

STANDARD FORM

The graph of the parabola represented by the quadratic function   y = a( x - p )² + q   has an axis of symmetry represented by the equation of the vertical line   x = p.

GENERAL FORM

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FACTORED FORM