Find the Domain of (x-12)²+4: Analyzing Positive and Negative Ranges

Quadratic Functions with Vertex Form Analysis

Find the positive and negative domains of the function below:

y=(x12)2+4 y=\left(x-12\right)^2+4

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Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Find the positive and negative domains of the function below:

y=(x12)2+4 y=\left(x-12\right)^2+4

2

Step-by-step solution

To find the positive and negative domains of the quadratic function y=(x12)2+4 y = (x - 12)^2 + 4 , let's proceed step-by-step:

  • Step 1: Identify the structure.
    The function is in vertex form y=(x12)2+4 y = (x - 12)^2 + 4 , which indicates a parabola that opens upwards, with vertex (12,4)(12, 4).
  • Step 2: Determine the minimum value.
    Since the vertex form shows the minimum value at y=4 y = 4 when x=12 x = 12 , the function never actually reaches negative values.
  • Step 3: Analyze positivity.
    Given that the minimum value y=4 y = 4 when x=12 x = 12 , and the parabola opens upwards, every possible value of x x results in y4 y \geq 4 . Therefore, the function is always positive for all x x .
  • Step 4: Conclusion on domains.
    The function has no negative values for any input. Thus, the negative domain is none, and the positive domain includes all values of x x . Therefore, we assert the positive domain is: all x x .

With our analysis complete, we can conclude that the positive and negative domains of the function are:

x<0: x < 0 : none

x>0: x > 0 : all x x

3

Final Answer

x<0: x < 0 : none

x>0: x > 0 : all x x

Key Points to Remember

Essential concepts to master this topic
  • Vertex Form: y=(x12)2+4 y = (x - 12)^2 + 4 has vertex at (12, 4)
  • Minimum Value: Parabola opens upward, so minimum y-value is 4
  • Check: Since minimum is y = 4 > 0, function is always positive ✓

Common Mistakes

Avoid these frequent errors
  • Confusing domains with ranges or positive/negative x-values
    Don't find where x > 0 or x < 0 = wrong focus! This question asks about where the function output (y-values) is positive or negative, not the input values. Always analyze the y-values: since y ≥ 4 for all x, the function is never negative.

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's the difference between domain and positive/negative domains?

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The domain is all possible x-values (input). The positive/negative domains refer to where the function output is positive or negative. For y=(x12)2+4 y = (x-12)^2 + 4 , domain is all real numbers, but y is never negative!

Why is the minimum value 4 and not 0?

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In vertex form y=(xh)2+k y = (x-h)^2 + k , the k value is the minimum (or maximum). Here k = 4, so the parabola's lowest point is at y = 4, not y = 0.

How do I know the parabola opens upward?

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Look at the coefficient of the squared term! Since (x12)2 (x-12)^2 has a positive coefficient of 1, the parabola opens upward. If it were negative, like (x12)2 -(x-12)^2 , it would open downward.

Can a quadratic function ever have no negative values?

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Absolutely! When a upward-opening parabola has its vertex above the x-axis (like ours with vertex at y = 4), the function is always positive. It never crosses or touches the x-axis.

What if the question asked for where x < 0 vs x > 0?

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That would be asking about input values, not output values. For x < 0: all negative x-values work. For x > 0: all positive x-values work. But this question asks about where the function output is positive or negative.

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