Math Problem Statement

Find the area of the shaded region. f left parenthesis x right parenthesisf(x)equals=x Superscript 4 Baseline minus 8 x cubed plus 24 x squaredx4−8x3+24x2​, g left parenthesis x right parenthesisg(x)equals=5 x plus 385x+38 -4 5 -10 50 x y ffleft parenthesis negative 1 comma 33 right parenthesis(−1,33)left parenthesis 2 comma 48 right parenthesis(2,48) g

A coordinate system has a horizontal x-axis labeled from negative negative 4 to 5 in increments of 1 and a vertical y-axis labeled from negative 10 to 50 in increments of 10. Two functions are graphed. From left to right, the graph of f falls while passing through (negative 1, 33), reaches a minimum at (0, 0), and then generally rises while passing through (2, 48). The graph of g is a line that rises from left to right, passing through (negative 1, 33) and (2, 48). The region above the graph of f and below the graph of g between x equals negative 1 and x equals 2 is shaded.

Solution

To find the area of the shaded region between the curves f(x)=x48x3+24x2f(x) = x^4 - 8x^3 + 24x^2 and g(x)=5x+38g(x) = 5x + 38 over the interval [1,2][-1, 2], follow these steps:

1. Find the Points of Intersection

The curves intersect at the given points (1,33)(-1, 33) and (2,48)(2, 48). This means that the area we want to compute is the region bounded by f(x)f(x) and g(x)g(x) from x=1x = -1 to x=2x = 2.

2. Set Up the Integral for the Area

The area between two curves, g(x)g(x) and f(x)f(x), over an interval [a,b][a, b] is given by:

Area=ab[g(x)f(x)]dx\text{Area} = \int_{a}^{b} \left[ g(x) - f(x) \right] \, dx

where g(x)g(x) is the upper curve and f(x)f(x) is the lower curve. Here:

  • g(x)=5x+38g(x) = 5x + 38
  • f(x)=x48x3+24x2f(x) = x^4 - 8x^3 + 24x^2
  • Interval: a=1a = -1 and b=2b = 2

3. Compute g(x)f(x)g(x) - f(x)

Let's find the difference between g(x)g(x) and f(x)f(x):

g(x)f(x)=(5x+38)(x48x3+24x2)=x4+8x324x2+5x+38g(x) - f(x) = (5x + 38) - (x^4 - 8x^3 + 24x^2) = -x^4 + 8x^3 - 24x^2 + 5x + 38

4. Set Up the Integral

Now, set up the definite integral from 1-1 to 22:

Area=12(x4+8x324x2+5x+38)dx\text{Area} = \int_{-1}^{2} \left( -x^4 + 8x^3 - 24x^2 + 5x + 38 \right) \, dx

5. Evaluate the Integral

To find the area, we integrate each term separately:

12(x4+8x324x2+5x+38)dx\int_{-1}^{2} \left( -x^4 + 8x^3 - 24x^2 + 5x + 38 \right) \, dx

Let's compute this step-by-step:

  1. Integral of x4-x^4: x4dx=x55\int -x^4 \, dx = -\frac{x^5}{5}

  2. Integral of 8x38x^3: 8x3dx=2x4\int 8x^3 \, dx = 2x^4

  3. Integral of 24x2-24x^2: 24x2dx=8x3\int -24x^2 \, dx = -8x^3

  4. Integral of 5x5x: 5xdx=5x22\int 5x \, dx = \frac{5x^2}{2}

  5. Integral of 3838: 38dx=38x\int 38 \, dx = 38x

Now, substitute the limits [1,2][-1, 2]:

[x55+2x48x3+5x22+38x]12\left[ -\frac{x^5}{5} + 2x^4 - 8x^3 + \frac{5x^2}{2} + 38x \right]_{-1}^{2}

6. Compute the Definite Integral

Evaluate at x=2x = 2:

255+2×248×23+5×222+38×2-\frac{2^5}{5} + 2 \times 2^4 - 8 \times 2^3 + \frac{5 \times 2^2}{2} + 38 \times 2

=325+3264+10+76=1505=30= -\frac{32}{5} + 32 - 64 + 10 + 76 = \frac{150}{5} = 30

Evaluate at x=1x = -1:

(1)55+2×(1)48×(1)3+5×(1)22+38×(1)-\frac{(-1)^5}{5} + 2 \times (-1)^4 - 8 \times (-1)^3 + \frac{5 \times (-1)^2}{2} + 38 \times (-1)

=15+2+8+5238=1215=24.2= \frac{1}{5} + 2 + 8 + \frac{5}{2} - 38 = -\frac{121}{5} = -24.2

Now compute the difference:

30(24.2)=54.230 - (-24.2) = 54.2

Thus, the area of the shaded region is:

54.2 square units.\boxed{54.2} \text{ square units.}


Do you want more details or have any questions? Here are some related problems you might find useful:

  1. What is the area between two curves over a different interval?
  2. How to find points of intersection between curves analytically?
  3. What happens if f(x)f(x) and g(x)g(x) swap their positions on the graph?
  4. How does changing coefficients in f(x)f(x) and g(x)g(x) alter the area?
  5. What is the geometric interpretation of integrals for areas?

Tip: Always confirm the order of f(x)f(x) and g(x)g(x) on the graph to correctly identify the upper and lower functions.

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Math Problem Analysis

Mathematical Concepts

Calculus
Integral Calculus
Area between Curves

Formulas

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

Theorems

Fundamental Theorem of Calculus

Suitable Grade Level

Grades 11-12 (AP Calculus, College-level Calculus)