Math Problem Statement

Calculate the area, in square units, bounded above by
f ( x )

x 2 + 8 x + 16 and
g ( x )

8 x + 80 and bounded below by the
x -axis over the interval
[ − 10 , − 4 ] .

Solution

To calculate the area bounded by the curves f(x)=x2+8x+16f(x) = x^2 + 8x + 16, g(x)=8x+80g(x) = 8x + 80, and the x-axis over the interval [10,4][-10, -4], we'll proceed as follows:

Step 1: Set up the area calculation

We need to determine the region where g(x)g(x) is above f(x)f(x) within the interval [10,4][-10, -4].

  1. Given functions:

    • f(x)=x2+8x+16f(x) = x^2 + 8x + 16
    • g(x)=8x+80g(x) = 8x + 80
  2. Interval:

    • The interval is [10,4][-10, -4].

Step 2: Find the points of intersection of f(x)f(x) and g(x)g(x) in the interval

Set f(x)=g(x)f(x) = g(x) to find the points of intersection:

x2+8x+16=8x+80x^2 + 8x + 16 = 8x + 80

Simplify by subtracting 8x+168x + 16 from both sides:

x2=64x^2 = 64

Taking the square root of both sides:

x=±8x = \pm 8

Within the interval [10,4][-10, -4], only x=8x = -8 is relevant. So, we have intersections at x=10x = -10 and x=8x = -8 for this interval.

Step 3: Set up the integrals

To find the area, split it into two regions from [10,8][-10, -8] and [8,4][-8, -4]:

  1. For [10,8][-10, -8], g(x)g(x) is above f(x)f(x).

    The area for this section is: A1=108(g(x)f(x))dxA_1 = \int_{-10}^{-8} \left( g(x) - f(x) \right) \, dx

  2. For [8,4][-8, -4], g(x)g(x) is still above f(x)f(x).

    The area for this section is: A2=84(g(x)f(x))dxA_2 = \int_{-8}^{-4} \left( g(x) - f(x) \right) \, dx

Step 4: Evaluate the integrals

Calculate g(x)f(x)g(x) - f(x):

g(x)f(x)=(8x+80)(x2+8x+16)g(x) - f(x) = (8x + 80) - (x^2 + 8x + 16) =x2+64= -x^2 + 64

Now we integrate x2+64-x^2 + 64 over the two intervals:

  1. For A1A_1: A1=108(x2+64)dxA_1 = \int_{-10}^{-8} (-x^2 + 64) \, dx

  2. For A2A_2: A2=84(x2+64)dxA_2 = \int_{-8}^{-4} (-x^2 + 64) \, dx

Step 5: Compute the integrals

Let's evaluate these integrals:

  1. Integral for A1A_1: A1=108(x2+64)dx=[x33+64x]108A_1 = \int_{-10}^{-8} (-x^2 + 64) \, dx = \left[ -\frac{x^3}{3} + 64x \right]_{-10}^{-8}

  2. Integral for A2A_2: A2=84(x2+64)dx=[x33+64x]84A_2 = \int_{-8}^{-4} (-x^2 + 64) \, dx = \left[ -\frac{x^3}{3} + 64x \right]_{-8}^{-4}

After evaluating these, add A1A_1 and A2A_2 to get the total area.

Let me calculate this explicitly.The total area bounded by the curves f(x)=x2+8x+16f(x) = x^2 + 8x + 16, g(x)=8x+80g(x) = 8x + 80, and the x-axis over the interval [10,4][-10, -4] is 7272 square units.

Would you like further details on the calculations, or do you have any questions?

Here are a few related questions to explore further:

  1. How would the area change if the interval was modified?
  2. What if f(x)f(x) and g(x)g(x) had different intersections in a broader interval?
  3. How does the shape of the parabolic function f(x)f(x) affect the bounded area?
  4. What are the implications if the x-axis was not considered as a boundary?
  5. How can we visualize these functions and the area on a graph?

Tip: When dealing with areas bounded by curves, always check where one function crosses over another to determine the correct boundaries and intervals.

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Math Problem Analysis

Mathematical Concepts

Calculus
Definite Integrals
Areas Bounded by Curves
Quadratic and Linear Functions

Formulas

Area between curves formula: ∫[a, b] (g(x) - f(x)) dx

Theorems

Fundamental Theorem of Calculus

Suitable Grade Level

Grades 11-12