Math Problem Statement

R is the region bounded by the functions f(x)=3e^x−1 and g(x)=x^2−1. Find the area of the region bounded by the functions on the interval [−1,1].

Solution

To find the area of the region bounded by the two functions f(x)=3ex1f(x) = 3e^x - 1 and g(x)=x21g(x) = x^2 - 1 on the interval [1,1][-1, 1], we follow these steps:

Step 1: Set up the integral

We need to find the points where f(x)=g(x)f(x) = g(x), which will help us identify the regions where one function is above the other.

So, we solve for the intersection points by setting: 3ex1=x213e^x - 1 = x^2 - 1 This simplifies to: 3ex=x23e^x = x^2

This equation doesn't have a simple analytical solution, so we check the interval [1,1][-1, 1] to see where the functions intersect by evaluating f(x)f(x) and g(x)g(x) at critical points.

Step 2: Evaluate at critical points

At x=1x = -1: f(1)=3e113(0.3679)11.10371=0.1037f(-1) = 3e^{-1} - 1 \approx 3(0.3679) - 1 \approx 1.1037 - 1 = 0.1037 g(1)=(1)21=0g(-1) = (-1)^2 - 1 = 0

At x=1x = 1: f(1)=3e113(2.718)1=8.1541=7.154f(1) = 3e^{1} - 1 \approx 3(2.718) - 1 = 8.154 - 1 = 7.154 g(1)=121=0g(1) = 1^2 - 1 = 0

At x=0x = 0: f(0)=3e01=3(1)1=2f(0) = 3e^{0} - 1 = 3(1) - 1 = 2 g(0)=021=1g(0) = 0^2 - 1 = -1

Based on these values, f(x)f(x) is above g(x)g(x) over the entire interval [1,1][-1, 1].

Step 3: Set up the integral for the area

The area between two curves is given by the integral of the difference between the functions: Area=11(f(x)g(x))dx\text{Area} = \int_{-1}^{1} (f(x) - g(x)) \, dx

Thus, we need to compute: Area=11((3ex1)(x21))dx\text{Area} = \int_{-1}^{1} \left( (3e^x - 1) - (x^2 - 1) \right) dx Simplifying the integrand: Area=11(3exx2)dx\text{Area} = \int_{-1}^{1} \left( 3e^x - x^2 \right) dx

Step 4: Compute the integral

We now split the integral into two parts: Area=113exdx11x2dx\text{Area} = \int_{-1}^{1} 3e^x \, dx - \int_{-1}^{1} x^2 \, dx

  1. The integral of 3ex3e^x: 113exdx=3[ex]11=3(e1e1)=3(2.7180.3679)=3(2.3501)=7.0503\int_{-1}^{1} 3e^x \, dx = 3 \left[ e^x \right]_{-1}^{1} = 3(e^1 - e^{-1}) = 3(2.718 - 0.3679) = 3(2.3501) = 7.0503

  2. The integral of x2x^2: 11x2dx=[x33]11=133(1)33=13(13)=23\int_{-1}^{1} x^2 \, dx = \left[ \frac{x^3}{3} \right]_{-1}^{1} = \frac{1^3}{3} - \frac{(-1)^3}{3} = \frac{1}{3} - \left(-\frac{1}{3}\right) = \frac{2}{3}

Step 5: Calculate the total area

Now, we subtract the results of the two integrals: Area=7.050323=7.05030.6667=6.3836\text{Area} = 7.0503 - \frac{2}{3} = 7.0503 - 0.6667 = 6.3836

Thus, the area of the region bounded by the functions f(x)=3ex1f(x) = 3e^x - 1 and g(x)=x21g(x) = x^2 - 1 on the interval [1,1][-1, 1] is approximately 6.3846.384.

Would you like a detailed explanation on any of the steps? Here are 5 questions to expand on:

  1. What happens if the functions intersect more than once on the interval?
  2. How do we handle finding intersection points when solving 3ex=x23e^x = x^2?
  3. Could we estimate the intersection points numerically?
  4. How do we integrate exponential and polynomial functions?
  5. What if one of the functions was below the x-axis?

Tip: Always check the bounds of integration carefully when working with areas between curves.

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Math Problem Analysis

Mathematical Concepts

Calculus
Area Between Curves
Integration

Formulas

Area between curves: ∫[a,b] (f(x) - g(x)) dx
Integral of exponential functions
Integral of polynomial functions

Theorems

Fundamental Theorem of Calculus

Suitable Grade Level

Grades 11-12