Mathematics Functions: Linear and Quadratic

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Questions and Answers

What is the slope and y-intercept of the function represented by the equation $f(x) = -3x + 5$?

  • Slope: -5, Y-intercept: 3
  • Slope: -3, Y-intercept: 5 (correct)
  • Slope: 3, Y-intercept: -5
  • Slope: 5, Y-intercept: -3

Which of the following equations represents a quadratic function that opens downwards?

  • $f(x) = 3x^2 + 2x$
  • $f(x) = 2x^2 - 5x + 4$
  • $f(x) = 4x^2 - 2x + 1$
  • $f(x) = -x^2 + 3$ (correct)

Determine the vertex of the quadratic function $f(x) = 2x^2 + 4x + 1$.

  • Vertex: (1, 1)
  • Vertex: (-1, 3)
  • Vertex: (-1, -1) (correct)
  • Vertex: (1, 3)

What can be inferred about the graph of the linear function $f(x) = 0.5x + 3$?

<p>The line crosses the y-axis at 3. (A)</p> Signup and view all the answers

In the quadratic function $f(x) = -3x^2 + 6x + 2$, what is the y-intercept?

<p>2 (B)</p> Signup and view all the answers

For the quadratic function $f(x) = x^2 + 6x + 8$, what is the axis of symmetry?

<p>$x = -3$ (B)</p> Signup and view all the answers

Which characteristic is true for the linear equation $f(x) = -5$?

<p>The line is horizontal. (C)</p> Signup and view all the answers

Which of the following functions has a positive slope?

<p>$f(x) = x - 3$ (D)</p> Signup and view all the answers

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Study Notes

Mathematics Functions

Linear Functions

  • Definition: A function that graphs to a straight line.
  • Standard Form:
    • ( f(x) = mx + b )
      • ( m ): slope (rate of change)
      • ( b ): y-intercept (where the line crosses the y-axis)
  • Characteristics:
    • Slope indicates the direction of the line:
      • Positive slope: line rises from left to right.
      • Negative slope: line falls from left to right.
      • Zero slope: horizontal line (no change).
    • Graph: Straight line; can be increasing or decreasing.
  • Examples:
    • ( f(x) = 2x + 3 ) (slope = 2, y-intercept = 3)
    • ( f(x) = -x + 1 ) (slope = -1, y-intercept = 1)

Quadratic Functions

  • Definition: A function that graphs to a parabola (U-shaped curve).
  • Standard Form:
    • ( f(x) = ax^2 + bx + c )
      • ( a ): coefficient of ( x^2 ) (determines direction of the parabola)
      • ( b ): coefficient of ( x )
      • ( c ): constant term (y-intercept)
  • Characteristics:
    • Opens upwards if ( a > 0 ) and downwards if ( a < 0 ).
    • Vertex: The highest or lowest point of the parabola, calculated using ( x = -\frac{b}{2a} ).
    • Axis of symmetry: Vertical line ( x = -\frac{b}{2a} ).
    • Y-intercept: Found by evaluating ( f(0) = c ).
  • Examples:
    • ( f(x) = x^2 - 4x + 3 ) (opens upwards, vertex at ( (2, -1) ))
    • ( f(x) = -2x^2 + 4x - 1 ) (opens downwards, vertex at ( (1, 1) ))

Linear Functions

  • Definition: Represents a relationship where a variable changes at a constant rate, producing a straight line on a graph.
  • Standard Form:
    • ( f(x) = mx + b )
      • ( m ): Represents the slope, indicating how steep the line is.
      • ( b ): The y-intercept, the point at which the line intersects the y-axis.
  • Slope Characteristics:
    • Positive slope indicates the line ascends from left to right.
    • Negative slope indicates the line descends from left to right.
    • Zero slope indicates a horizontal line, signifying no change in the y-value with different x-values.
  • Graph Properties: Consists of straight lines that can be either increasing or decreasing based on the slope.
  • Examples:
    • For ( f(x) = 2x + 3 ): slope is 2 (line rises) and y-intercept is 3 (crosses y-axis at (0,3)).
    • For ( f(x) = -x + 1 ): slope is -1 (line falls) and y-intercept is 1 (crosses y-axis at (0,1)).

Quadratic Functions

  • Definition: Describe a parabolic relationship, yielding a U-shaped graph.
  • Standard Form:
    • ( f(x) = ax^2 + bx + c )
      • ( a ): Determines whether the parabola opens upwards (if ( a > 0 )) or downwards (if ( a < 0 )).
      • ( b ): Influences the position of the vertex.
      • ( c ): The y-intercept, where the parabola crosses the y-axis.
  • Vertex: The highest or lowest point on the parabola, calculated using ( x = -\frac{b}{2a} ).
  • Axis of Symmetry: A vertical line represented by ( x = -\frac{b}{2a} ) that divides the parabola into two mirror-image halves.
  • Y-intercept: Detected by evaluating the function at zero, ( f(0) = c ).
  • Examples:
    • For ( f(x) = x^2 - 4x + 3 ): opens upwards and has a vertex at ( (2, -1) ).
    • For ( f(x) = -2x^2 + 4x - 1 ): opens downwards and has a vertex at ( (1, 1) ).

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