Find the Domain of y=(x-1)²+5: Analyzing Positive and Negative Inputs

Quadratic Functions with Domain Analysis

Find the positive and negative domains of the function below:

y=(x1)2+5 y=\left(x-1\right)^2+5

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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=(x1)2+5 y=\left(x-1\right)^2+5

2

Step-by-step solution

To solve this problem, we need to analyze the function y=(x1)2+5 y = (x-1)^2 + 5 , which is a quadratic in vertex form.

Step 1: Identify the Vertex and Orientation
The function is given as y=(x1)2+5 y = (x-1)^2 + 5 , which is in the form y=a(xh)2+k y = a(x-h)^2 + k . Here, h=1 h = 1 and k=5 k = 5 , meaning the vertex of the parabola is at (1,5) (1, 5) . Because a=1 a = 1 (which is positive), the parabola opens upwards.

Step 2: Determine the Minimum Value of y y
Since the parabola opens upwards, the minimum value of y y occurs at the vertex. At the vertex (1,5) (1, 5) , the value of y y is 5.

Step 3: Analyze Positive and Negative Values of y y
The minimum value of y y is 5, which indicates that y y is always greater than zero. Thus, for all real values of x x , y y remains positive.

Conclusion:
Since the function y=(x1)2+5 y = (x-1)^2 + 5 has no negative values and is always positive:

x<0: x < 0 : none

x>0: x > 0 : all x x

Therefore, 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=a(xh)2+k y = a(x-h)^2 + k shows vertex at (h,k)
  • Technique: Minimum y-value is 5 since parabola opens upward
  • Check: Test x = 1: y=(11)2+5=5>0 y = (1-1)^2 + 5 = 5 > 0

Common Mistakes

Avoid these frequent errors
  • Confusing domain with range
    Don't find where y is positive/negative instead of the actual domain = wrong interpretation! The question asks about positive and negative domains, meaning where y-values are positive or negative. Always analyze the range (y-values) to determine when the function is positive or 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 (which is all real numbers here). The positive domain means where y > 0, and negative domain means where y < 0.

Why is the minimum value 5 and not 0?

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The vertex is at (1, 5), so the parabola's lowest point has y = 5. Since (x1)2 (x-1)^2 is always ≥ 0, adding 5 makes y always ≥ 5.

How do I know the parabola opens upward?

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Look at the coefficient of the squared term. Since (x1)2 (x-1)^2 has coefficient +1 (positive), the parabola opens upward.

Can this function ever equal zero?

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No! The minimum value is 5, so y=(x1)2+5 y = (x-1)^2 + 5 is always greater than or equal to 5. It never reaches zero or becomes negative.

What if the question asked for where y < 0?

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Since the function is always positive (y ≥ 5), there are no values of x where y < 0. The answer would be "none" or "no solution."

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