Domain Analysis: Solving (x-6)² + 8 Function Boundaries

Quadratic Functions with Vertex Form Analysis

Find the positive and negative domains of the function below:

y=(x6)2+8 y=\left(x-6\right)^2+8

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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=(x6)2+8 y=\left(x-6\right)^2+8

2

Step-by-step solution

To solve this problem, we will explore the behavior of the quadratic function y=(x6)2+8 y = (x-6)^2 + 8 .

The function is in vertex form, y=(xh)2+k y = (x-h)^2 + k , where the vertex of the parabola is at (h,k)=(6,8) (h, k) = (6, 8) . The parabola opens upwards because the squared term, (x6)2 (x-6)^2 , has a positive coefficient (which is 1).

Given this upward-opening parabola, the minimum value of y y is 8 8 , which occurs when x=6 x = 6 . As a result, the quadratic expression y=(x6)2+8 y = (x-6)^2 + 8 will always yield non-negative values, actually, specifically, it will always yield positive values y8 y \geq 8 across its entire domain of real numbers. Therefore, there are no negative values for y y in the range of this function, as the minimum bound itself is positive.

Thus, the analysis tells us:

  • Negative domain x<0 x < 0 : None, meaning no part of the range y y becomes negative.
  • Positive domain x>0 x > 0 : All x x , indicating that y y is always positive or zero, overriding negative conditions.

Therefore, the solution for the domains is:

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=(xh)2+k y = (x-h)^2 + k has vertex at (h, k)
  • Range Analysis: Minimum y-value is 8 when x = 6, so y8 y \geq 8
  • Domain Check: Function never equals zero or negative values ✓

Common Mistakes

Avoid these frequent errors
  • Confusing domain with range when analyzing positive/negative values
    Don't look for where x is positive or negative = wrong interpretation! The question asks about where the function OUTPUT (y-values) is positive or negative. Always analyze the range of y-values, not the domain of x-values.

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 'positive and negative domains' actually mean?

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This is asking where the function values (y-values) are positive or negative, not where x is positive or negative. Look at the output of the function!

How do I find the minimum value of a quadratic in vertex form?

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In y=(xh)2+k y = (x-h)^2 + k , the minimum value is k (the constant term). Since (xh)20 (x-h)^2 \geq 0 , the smallest y can be is k.

Why can't this function have negative y-values?

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Since (x6)20 (x-6)^2 \geq 0 for all real x, we have y=(x6)2+88 y = (x-6)^2 + 8 \geq 8 . The function is always at least 8, so it never reaches zero or negative values.

Does the vertex being at x = 6 matter for this problem?

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Not directly! The x-coordinate of the vertex doesn't affect whether y-values are positive or negative. What matters is the y-coordinate (8) being the minimum value.

How do I verify that y is always positive?

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Pick any x-value and calculate: try x = 0, then y=(06)2+8=36+8=44>0 y = (0-6)^2 + 8 = 36 + 8 = 44 > 0 . Try x = 10, then y=(106)2+8=16+8=24>0 y = (10-6)^2 + 8 = 16 + 8 = 24 > 0 . Always positive!

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