Turning Point

Definition

A turning point is a critical point in a function or graph where the direction of the curve changes from increasing to decreasing, or vice versa. It represents a significant transition in the behavior of the function and is an important feature in the analysis of parabolic curves.

5 Must Know Facts For Your Next Test

1. The turning point of a parabola corresponds to the vertex, which is the point where the parabola changes from increasing to decreasing or vice versa.
2. The x-coordinate of the turning point is the solution to the equation $ax^2 + bx + c = 0$, where $a$, $b$, and $c$ are the coefficients of the quadratic function.
3. The y-coordinate of the turning point is found by substituting the x-coordinate of the turning point into the original quadratic function.
4. The turning point represents the maximum or minimum value of the parabolic function, depending on the sign of the leading coefficient $a$.
5. Identifying the turning point is crucial in understanding the behavior and properties of a parabolic function, such as its domain, range, and symmetry.

Review Questions

• Explain the relationship between the turning point and the vertex of a parabola.
  • The turning point and the vertex of a parabola are the same point. The turning point is the critical point where the direction of the parabolic curve changes, and this point corresponds to the vertex, which is the highest or lowest point of the parabola. The x-coordinate of the turning point is the solution to the equation $ax^2 + bx + c = 0$, and the y-coordinate is found by substituting the x-coordinate into the original quadratic function. Identifying the turning point/vertex is essential for understanding the properties and behavior of a parabolic function.
• Describe how the concavity of a parabola is related to the turning point.
  • The concavity of a parabola, whether it is concave up or concave down, is determined by the sign of the leading coefficient $a$ in the quadratic function $ax^2 + bx + c$. If $a$ is positive, the parabola is concave up, and the turning point represents the minimum value of the function. If $a$ is negative, the parabola is concave down, and the turning point represents the maximum value of the function. The turning point, or vertex, is the point where the concavity changes direction, marking the critical transition in the behavior of the parabolic curve.
• Analyze how the turning point of a parabola can be used to determine the function's symmetry and range.
  • The turning point of a parabola, which corresponds to the vertex, is a key feature for understanding the symmetry and range of the function. Since the vertex is the point of symmetry, the turning point divides the parabola into two symmetric halves. This means that the function is symmetric about the vertical line passing through the turning point, the axis of symmetry. Additionally, the turning point represents the maximum or minimum value of the function, which determines the range of the parabolic curve. If the turning point is a maximum, the range will be all $y$ values less than or equal to the $y$-coordinate of the turning point. If the turning point is a minimum, the range will be all $y$ values greater than or equal to the $y$-coordinate of the turning point. Understanding the turning point's relationship to symmetry and range is crucial for analyzing the properties and behavior of parabolic functions.

Related terms

Vertex: The vertex of a parabola is the point where the parabola changes direction, representing the highest or lowest point of the curve.

Axis of Symmetry: The axis of symmetry of a parabola is the vertical line that passes through the vertex, dividing the parabola into two symmetric halves.

Concavity: The concavity of a parabola refers to the direction of the curve, either opening upward (concave up) or downward (concave down).