Axis of Symmetry

Definition

The axis of symmetry is a line that divides a graph or equation into two equal halves, where each side is a reflection of the other. This concept is particularly important in the study of quadratic equations and their graphical representations.

5 Must Know Facts For Your Next Test

1. The axis of symmetry of a quadratic equation $ax^2 + bx + c = 0$ is given by the formula $x = -b/(2a)$.
2. The axis of symmetry passes through the vertex of the parabolic graph of a quadratic equation.
3. Knowing the axis of symmetry is crucial for solving quadratic equations using the square root property, completing the square, and the quadratic formula.
4. The axis of symmetry is also important in applications involving quadratic equations, such as optimization problems.
5. When graphing quadratic equations in two variables, the axis of symmetry is a vertical line that passes through the vertex of the parabola.

Review Questions

• Explain how the axis of symmetry is used in solving quadratic equations using the square root property.
  • The axis of symmetry plays a crucial role in solving quadratic equations using the square root property. By identifying the axis of symmetry, which is given by $x = -b/(2a)$, you can then use this information to determine the two solutions to the equation. Specifically, the square root property states that the solutions to a quadratic equation $ax^2 + bx + c = 0$ are $x = (-b \pm \sqrt{b^2 - 4ac})/(2a)$. The axis of symmetry, $x = -b/(2a)$, represents the midpoint between these two solutions, allowing you to efficiently find the roots of the equation.
• Describe how the axis of symmetry is used when solving quadratic equations by completing the square.
  • When solving quadratic equations by completing the square, the axis of symmetry is a crucial piece of information. By first identifying the axis of symmetry, given by $x = -b/(2a)$, you can then use this value to rewrite the quadratic equation in standard form, $a(x - h)^2 + k$, where $(h, k)$ represents the vertex of the parabola. This transformation allows you to more easily solve the equation by completing the square and finding the two solutions that are equidistant from the axis of symmetry.
• Explain how the axis of symmetry is utilized when graphing quadratic equations in two variables.
  • When graphing quadratic equations in two variables, the axis of symmetry plays a vital role in determining the shape and orientation of the parabolic graph. The axis of symmetry is a vertical line that passes through the vertex of the parabola, dividing the graph into two equal halves. By identifying the equation of the axis of symmetry, given by $x = -b/(2a)$, you can accurately sketch the parabolic graph and determine important features such as the vertex, the direction of opening, and the range of the function.

Related terms

Quadratic Equation: A polynomial equation of the form $ax^2 + bx + c = 0$, where $a$, $b$, and $c$ are real numbers and $a \neq 0.

Vertex: The point on a parabolic graph where the graph changes direction, representing the minimum or maximum value of the function.

Parabola: The U-shaped graph of a quadratic equation, which is symmetric about its axis of symmetry.