The axis of symmetry for y = ax^2 + bx + c is given by which equation?

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Multiple Choice

The axis of symmetry for y = ax^2 + bx + c is given by which equation?

Explanation:
The axis of symmetry is the vertical line that passes through the parabola’s vertex. For y = ax^2 + bx + c, the x-coordinate of the vertex can be found by completing the square: y = a[(x + b/(2a))^2] - b^2/(4a) + c, so the vertex occurs at x = -b/(2a). Equivalently, taking the derivative y' = 2ax + b and setting it to zero gives x = -b/(2a). Therefore the axis of symmetry is x = -b/(2a). Remember, it’s a vertical line; a horizontal line like y = something would not be the axis.

The axis of symmetry is the vertical line that passes through the parabola’s vertex. For y = ax^2 + bx + c, the x-coordinate of the vertex can be found by completing the square: y = a[(x + b/(2a))^2] - b^2/(4a) + c, so the vertex occurs at x = -b/(2a). Equivalently, taking the derivative y' = 2ax + b and setting it to zero gives x = -b/(2a). Therefore the axis of symmetry is x = -b/(2a). Remember, it’s a vertical line; a horizontal line like y = something would not be the axis.

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