Find the Domain of y=(x+2)²+12: Positive and Negative Regions

Quadratic Functions with Positive Domain Analysis

Find the positive and negative domains of the function below:

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

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

2

Step-by-step solution

To find the positive and negative domains of the function y=(x+2)2+12 y = (x+2)^2 + 12 , follow these steps:

  • Identify the vertex of the function: The vertex form is y=(x+2)2+12 y = (x+2)^2 + 12 , hence the vertex is at (2,12) (-2, 12) .
  • Determine the parabola's direction: Given the coefficient of (x+2)2 (x+2)^2 is positive, the parabola opens upwards.
  • Consider the vertex's role: At x=2 x = -2 , the minimum value of y y is 12. Since the parabola opens upwards from there, y12 y \geq 12 for all x x .
  • Analyze positivity/negativity: Since the minimum y y -value is 12, the function is always positive for all real x x , and hence it is not negative for any x x .

Therefore, the positive domain is all x x , and there is no negative domain. The final choice 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: Identify vertex from y = (x - h)² + k
  • Minimum Value: At x = -2, y = 12 (lowest point)
  • Verification: Check y-values: (0+2)² + 12 = 16 > 0 ✓

Common Mistakes

Avoid these frequent errors
  • Confusing domain with range or positive/negative regions
    Don't mix up domain (x-values) with where the function is positive/negative = wrong classification! Domain is all possible x-values, while positive/negative regions describe where y-values are above or below zero. Always analyze the y-output values to determine positive and negative regions.

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

What does 'positive domain' actually mean?

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The term is asking for x-values where y is positive, not the domain itself. Since y=(x+2)2+12 y = (x+2)^2 + 12 always gives positive y-values, the answer is all real x.

How do I find the minimum value of this parabola?

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Use the vertex form! In y=(x+2)2+12 y = (x+2)^2 + 12 , the vertex is at (-2, 12). Since the coefficient of the squared term is positive, this vertex gives the minimum y-value of 12.

Why is there no negative region for this function?

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Because the minimum y-value is 12, and the parabola opens upward from there. Since 12 > 0, all y-values are positive. The function never dips below the x-axis.

Can I solve this by setting y = 0?

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You could try, but (x+2)2+12=0 (x+2)^2 + 12 = 0 has no real solutions! This confirms the function is never zero or negative, only positive.

What if the constant term was negative instead?

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If we had y=(x+2)25 y = (x+2)^2 - 5 , then the minimum would be -5, creating both positive and negative regions. The sign of the constant term at the vertex determines this!

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