Use the zeros to determine which of the following graphs is a sketch of the polynomial f(x)=−x(x+2)2.(1 point)

Responses

A curve passes through quadrants 2 and 4 on a coordinate plane with the x-axis ranging from negative 6 to 2 in unit increments.
Image with alt text: A curve passes through quadrants 2 and 4 on a coordinate plane with the x-axis ranging from negative 6 to 2 in unit increments.

A downward-opening parabola is plotted on a coordinate plane with the x-axis ranging from negative 4 to 2 in unit increments.
Image with alt text: A downward-opening parabola is plotted on a coordinate plane with the x-axis ranging from negative 4 to 2 in unit increments.

A curve passes through quadrants 2 and 4 on a coordinate plane with the x-axis ranging from negative 2 to 6 in unit increments.
Image with alt text: A curve passes through quadrants 2 and 4 on a coordinate plane with the x-axis ranging from negative 2 to 6 in unit increments.

A curve with arrows at both the ends is plotted on a coordinate plane. The x-axis ranges from negative 6 to 2 in unit increments. The y-axis does not show any values.

1 answer

To analyze the polynomial \( f(x) = -x(x+2)^2 \), we first need to identify its zeros and the behavior of the graph at those points.

  1. Finding the Zeros:

    • The polynomial is factored as \( f(x) = -x(x+2)^2 \).
    • The zeros occur when \( f(x) = 0 \):
      • \( x = 0 \) (one zero)
      • \( (x + 2)^2 = 0 \) gives \( x = -2 \) (with a multiplicity of 2).
    • Thus, the zeros are \( x = 0 \) and \( x = -2 \).
  2. Determining the Behavior Around the Zeros:

    • Since the leading coefficient of the polynomial is negative, the graph opens downward.
    • At \( x = 0 \) (odd multiplicity), the graph will cross the x-axis.
    • At \( x = -2 \) (even multiplicity), the graph will touch the x-axis but will not cross it.
  3. Finding the End Behavior:

    • As \( x \to \infty \), \( f(x) \to -\infty \) (because the leading term is negative).
    • As \( x \to -\infty \), \( f(x) \to -\infty \).

Considering this information:

  • The graph will start high in quadrant 2, drop down to touch the x-axis at \( x = -2 \), then continue downward, crossing the x-axis at \( x = 0 \) before going down into quadrant 4.

Given these characteristics, we can eliminate options based on their descriptions:

  • The second option (downward-opening parabola) does not match our findings about the multiplicities and specific shape around the zeros.
  • The graphs with curves passing through quadrants 2 and 4 indicate that the graph likely touches at -2 and crosses at 0, which is consistent with our analysis.

Thus, the correct response would be the one that describes a curve passing through quadrants 2 and 4, indicating it properly touches the x-axis at \( x = -2 \) and crosses it at \( x = 0 \).

Recommended Response: A curve passes through quadrants 2 and 4 on a coordinate plane with the x-axis ranging from negative 2 to 6 in unit increments.