Calculate Negative Area of f(x) = x² - 4: Below X-Axis Region

Find the negative area of the function

f(x)=x24 f(x)=x^2-4

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Step-by-step video solution

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00:00 Found negative domain of the function
00:03 Looking at X² coefficient, positive so function is happy
00:10 Negative domain is actually below X-axis
00:15 Therefore set Y=0 to find intersection points with X-axis
00:20 Isolate X
00:24 Extract root
00:28 When extracting root there are 2 solutions (positive and negative)
00:35 These are the intersection points with X-axis
00:41 Let's mark the intersection points with X-axis
00:54 The positive domain is above X-axis
00:59 The negative domain is below X-axis
01:05 Find the domain where the function is negative
01:09 And this is the solution to the question

Step-by-step written solution

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1

Understand the problem

Find the negative area of the function

f(x)=x24 f(x)=x^2-4

2

Step-by-step solution

To determine the interval where the function f(x)=x24 f(x) = x^2 - 4 is negative, follow these steps:

  • Step 1: Identify the roots of the function by solving x24=0 x^2 - 4 = 0 .
    x2=4 x^2 = 4 yields x=2 x = 2 and x=2 x = -2 .
  • Step 2: Consider the intervals created by these roots: (,2) (-\infty, -2) , (2,2) (-2, 2) , and (2,) (2, \infty) .
  • Step 3: Determine the sign of f(x) f(x) in each interval by selecting a test point from each:
    • For x=0 x = 0 in (2,2) (-2, 2) :
      f(0)=024=4 f(0) = 0^2 - 4 = -4 (Negative)
    • For x=3 x = -3 in (,2) (-\infty, -2) :
      f(3)=(3)24=94=5 f(-3) = (-3)^2 - 4 = 9 - 4 = 5 (Positive)
    • For x=3 x = 3 in (2,) (2, \infty) :
      f(3)=324=94=5 f(3) = 3^2 - 4 = 9 - 4 = 5 (Positive)
  • Step 4: The function f(x) f(x) is negative only in the interval (2,2) (-2, 2) .

Consequently, the interval where the function has negative values is 2<x<2 -2 < x < 2 , which aligns with choice 2 in the provided options.

3

Final Answer

2<x<2 -2 < x < 2

Practice Quiz

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One function

\( y=-2x^2-3 \)

to the corresponding graph:

333333-3-3-3333-3-3-3-3-3-31234

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