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

Question

Find the positive and negative domains of the function below:

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

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}

Answer

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

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