Parabola Analysis: Relationship Between Vertex Position and Function Values

Quadratic Functions with Vertex Analysis

If the parabola is smiling and its vertex is above the x-axis, then it is always negative.

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Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

If the parabola is smiling and its vertex is above the x-axis, then it is always negative.

2

Step-by-step solution

To solve this problem, we'll analyze what is implied if the parabola is smiling (opening upwards) and if its vertex is located above the x-axis:

  • Step 1: Identify properties of the quadratic function. A "smiling" parabola in the form y=a(xh)2+ky = a(x-h)^2 + k with a>0a > 0 means the parabola opens upwards. The vertex (h,k)(h, k) will determine its intersection with the x-axis.
  • Step 2: Evaluate the impact of the vertex's location. If the vertex is above the x-axis, then k>0k > 0, indicating the vertex point itself is positive.
  • Step 3: Assess when the function is negative. For an upwards-facing parabola, yy takes on positive values when above the x-axis and negative values when below. If the vertex is above the x-axis, the quadratic will indeed become positive as xx moves away from the vertex, indicating that it cannot always be negative.
  • Step 4: Interpretation of statement: Given that the parabola could cross the x-axis in some regions other than the vertex and will achieve positive yy-values whenever the vertex is above the x-axis, the statement "the parabola is always negative" is incorrect.

Therefore, the given statement is Incorrect.

3

Final Answer

Incorrect

Key Points to Remember

Essential concepts to master this topic
  • Direction: Smiling parabola opens upward with positive leading coefficient
  • Vertex Impact: When vertex k > 0, minimum value equals k
  • Check Sign: Upward parabola with vertex above x-axis has positive minimum ✓

Common Mistakes

Avoid these frequent errors
  • Confusing vertex location with function sign
    Don't assume vertex above x-axis means function is always negative = wrong conclusion! The vertex gives the minimum value for upward parabolas. Always remember: if vertex is above x-axis, the entire parabola stays positive.

Practice Quiz

Test your knowledge with interactive questions

The graph of the function below does not intersect the \( x \)-axis.

The parabola's vertex is marked A.

Find all values of \( x \) where
\( f\left(x\right) > 0 \).

AAAX

FAQ

Everything you need to know about this question

What does it mean when a parabola is 'smiling'?

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A smiling parabola opens upward, like a U-shape. This happens when the coefficient of x2 x^2 is positive. The vertex is the lowest point on the graph.

If the vertex is above the x-axis, what does that tell us?

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When the vertex is above the x-axis, the minimum value of the parabola is positive. Since an upward-opening parabola only gets higher from its vertex, all function values are positive.

Can an upward parabola ever be negative?

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Yes! If the vertex is below the x-axis, parts of the parabola will be negative. But if the vertex is above the x-axis, the entire parabola stays positive.

How do I find where a parabola crosses the x-axis?

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Set the function equal to zero: y=0 y = 0 . If the vertex is above the x-axis for an upward parabola, there are no real solutions - it never crosses!

What's the difference between vertex form and standard form?

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Vertex form is y=a(xh)2+k y = a(x-h)^2 + k where (h,k) is the vertex. Standard form is y=ax2+bx+c y = ax^2 + bx + c . Vertex form makes it easier to see the vertex location!

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