Parabola Function Analysis: Finding Positive Values Above X-Axis

Parabola Properties with Non-Intersecting X-axis

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

The parabola's vertex is marked A.

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

AAAX

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Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

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

The parabola's vertex is marked A.

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

AAAX

2

Step-by-step solution

Based on the given graph characteristics, we conclude that the parabola never intersects the x x -axis and is therefore entirely above it due to opening upwards. This means the function is always positive for every x x .

Thus, the correct choice is:

  • Choice 3: The domain is always positive.

Therefore, the solution to the problem is the domain is always positive.

3

Final Answer

The domain is always positive.

Key Points to Remember

Essential concepts to master this topic
  • Rule: Parabolas above x-axis have all positive function values
  • Technique: Check vertex position: if vertex above x-axis, entire parabola positive
  • Check: No x-intercepts means f(x) > 0 for all x values ✓

Common Mistakes

Avoid these frequent errors
  • Looking for specific x-values where function is positive
    Don't try to find individual x-values like x > A or x < A = missing the big picture! When a parabola doesn't intersect the x-axis and opens upward, every point is above zero. Always recognize that the entire domain gives positive values.

Practice Quiz

Test your knowledge with interactive questions

The graph of the function below intersects the X-axis at points A and B.

The vertex of the parabola is marked at point C.

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

AAABBBCCCX

FAQ

Everything you need to know about this question

How can I tell if a parabola is always positive?

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Look for two key signs: the parabola opens upward (U-shape) and never touches the x-axis. If both are true, then f(x) > 0 for all x values!

What does 'domain is always positive' mean?

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It means that no matter what x-value you choose, the function output will always be greater than zero. The parabola stays completely above the x-axis.

Why isn't the answer related to the vertex point A?

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The vertex A shows the lowest point of the parabola. Since even this lowest point is above the x-axis, every other point must also be positive. It's not about being greater or less than A!

How is this different from parabolas that cross the x-axis?

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Parabolas that cross the x-axis have some negative and some positive regions. But this parabola never crosses, so there are no negative regions at all.

Can I verify this without the graph?

+

Yes! If you have the equation, check the discriminant. When discriminant < 0 and the coefficient of x2 x^2 is positive, the parabola never touches the x-axis and stays positive.

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