Find the Domain of (x+10)²-3: Determining Valid Input Values

Quadratic Functions with Domain Analysis

Find the positive and negative domains of the function below:

y=(x+10)23 y=\left(x+10\right)^2-3

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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+10)23 y=\left(x+10\right)^2-3

2

Step-by-step solution

To solve this problem, we need to determine when y=(x+10)23 y = (x+10)^2 - 3 is greater than and less than zero.

Start by finding the roots of the equation:

Set y=0 y = 0 :

(x+10)23=0(x+10)^2 - 3 = 0

Rearrange the equation to find:

(x+10)2=3(x+10)^2 = 3

Take the square root of both sides:

x+10=±3x + 10 = \pm\sqrt{3}

Solving these gives:

  • x=10+3x = -10 + \sqrt{3}
  • x=103x = -10 - \sqrt{3}

These roots divide the number line into three intervals:

  • (,103)(-\infty, -10 - \sqrt{3})
  • (103,10+3)(-10 - \sqrt{3}, -10 + \sqrt{3})
  • (10+3,)(-10 + \sqrt{3}, \infty)

Test each interval to determine where the function is positive or negative:

For x<103 x < -10 - \sqrt{3} : Choose x=11 x = -11

Then: y=((11+10)23)=13=2 y = ((-11 + 10)^2 - 3) = 1 - 3 = -2

So, y<0 y < 0 in the interval (,103)(-\infty, -10 - \sqrt{3}).

For 103<x<10+3 -10 - \sqrt{3} < x < -10 + \sqrt{3} : Choose x=10 x = -10

Then: y=((10+10)23)=03=3 y = ((-10 + 10)^2 - 3) = 0 - 3 = -3

So, y<0 y < 0 in the interval (103,10+3)(-10 - \sqrt{3}, -10 + \sqrt{3}).

For x>10+3 x > -10 + \sqrt{3} : Choose x=0 x = 0

Then: y=((0+10)23)=1003=97 y = ((0 + 10)^2 - 3) = 100 - 3 = 97

So, y>0 y > 0 in the interval (10+3,)(-10 + \sqrt{3}, \infty).

Therefore, the positive domain is x>10+3 x > -10 + \sqrt{3} while the negative domain is x<10+3 x < -10 + \sqrt{3} .

Using the analysis above and applying it to the choices, the correct response is:

x<0:103<x<10+3 x < 0 : -10-\sqrt{3} < x < -10+\sqrt{3}

x>10+3 x > -10+\sqrt{3} or x>0:x<103 x > 0 : x < -10-\sqrt{3}

3

Final Answer

x<0:103<x<103 x < 0 : -10-\sqrt{3} < x < -10-\sqrt{3}

x>10+3 x > -10+\sqrt{3} or x>0:x<103 x > 0 : x < -10-\sqrt{3}

Key Points to Remember

Essential concepts to master this topic
  • Domain Rule: All real numbers are valid inputs for polynomial functions
  • Technique: Find zeros by setting (x+10)23=0 (x+10)^2 - 3 = 0 to get x=10±3 x = -10 \pm \sqrt{3}
  • Check: Test values in each interval to verify positive/negative regions ✓

Common Mistakes

Avoid these frequent errors
  • Confusing domain with range or positive/negative regions
    Don't think the domain excludes certain x-values because the function is negative there = wrong concept! The domain of a polynomial is always all real numbers. Always remember domain means valid inputs, while positive/negative regions show where outputs are above or below zero.

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 regions?

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Domain is all possible x-values you can input (for polynomials, that's all real numbers). Positive/negative regions tell you where the function's output is above or below zero.

Why do I need to find the zeros first?

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The zeros are where the function equals zero, creating boundary points. These points divide the number line into intervals where the function is either entirely positive or entirely negative.

How do I test which intervals are positive or negative?

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Pick any test value from each interval and substitute it into the function. If you get a positive result, that entire interval is positive. If negative, the whole interval is negative.

Can a quadratic function change from positive to negative multiple times?

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A quadratic can change sign at most twice because it has at most 2 zeros. The pattern is always: positive → negative → positive (or the reverse), creating at most 3 regions.

What if I get confused by the square root answers?

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Remember: 10311.7 -10 - \sqrt{3} \approx -11.7 and 10+38.3 -10 + \sqrt{3} \approx -8.3 . Use these decimal approximations to help visualize the intervals on a number line.

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