Math Problem Statement

Solution

To find the average value of the function f(x)=3x2e2xf(x) = 3x^2 e^{2x} on the interval [0,1][0, 1], we use the formula for the average value of a function ff over the interval [a,b][a, b]:

Average value=1baabf(x)dx\text{Average value} = \frac{1}{b-a} \int_a^b f(x) \, dx

In this case, a=0a = 0 and b=1b = 1. Thus, we have:

Average value=110013x2e2xdx=013x2e2xdx\text{Average value} = \frac{1}{1-0} \int_0^1 3x^2 e^{2x} \, dx = \int_0^1 3x^2 e^{2x} \, dx

To solve this integral, we will use integration by parts. Let u=x2u = x^2 and dv=3e2xdxdv = 3e^{2x} \, dx. Then, we have du=2xdxdu = 2x \, dx and v=32e2xv = \frac{3}{2} e^{2x}.

Using integration by parts formula udv=uvvdu\int u \, dv = uv - \int v \, du:

3x2e2xdx=(x232e2x)(32e2x2x)dx\int 3x^2 e^{2x} \, dx = \left( x^2 \cdot \frac{3}{2} e^{2x} \right) - \int \left( \frac{3}{2} e^{2x} \cdot 2x \right) dx

=32x2e2x3xe2xdx= \frac{3}{2} x^2 e^{2x} - 3 \int x e^{2x} \, dx

Now, we need to integrate xe2xx e^{2x}. Again, we use integration by parts. Let u=xu = x and dv=e2xdxdv = e^{2x} \, dx. Then, du=dxdu = dx and v=12e2xv = \frac{1}{2} e^{2x}:

xe2xdx=(x12e2x)(12e2x1)dx\int x e^{2x} \, dx = \left( x \cdot \frac{1}{2} e^{2x} \right) - \int \left( \frac{1}{2} e^{2x} \cdot 1 \right) dx

=12xe2x12e2xdx= \frac{1}{2} x e^{2x} - \frac{1}{2} \int e^{2x} \, dx

=12xe2x1212e2x=12xe2x14e2x= \frac{1}{2} x e^{2x} - \frac{1}{2} \cdot \frac{1}{2} e^{2x} = \frac{1}{2} x e^{2x} - \frac{1}{4} e^{2x}

Putting it all together:

3x2e2xdx=32x2e2x3(12xe2x14e2x)\int 3x^2 e^{2x} \, dx = \frac{3}{2} x^2 e^{2x} - 3 \left( \frac{1}{2} x e^{2x} - \frac{1}{4} e^{2x} \right)

=32x2e2x32xe2x+34e2x= \frac{3}{2} x^2 e^{2x} - \frac{3}{2} x e^{2x} + \frac{3}{4} e^{2x}

Now, we evaluate this expression from 00 to 11:

[32x2e2x32xe2x+34e2x]01\left[ \frac{3}{2} x^2 e^{2x} - \frac{3}{2} x e^{2x} + \frac{3}{4} e^{2x} \right]_0^1

=(3212e21321e21+34e21)(3202e20320e20+34e20)= \left( \frac{3}{2} \cdot 1^2 \cdot e^{2 \cdot 1} - \frac{3}{2} \cdot 1 \cdot e^{2 \cdot 1} + \frac{3}{4} e^{2 \cdot 1} \right) - \left( \frac{3}{2} \cdot 0^2 \cdot e^{2 \cdot 0} - \frac{3}{2} \cdot 0 \cdot e^{2 \cdot 0} + \frac{3}{4} e^{2 \cdot 0} \right)

=(32e232e2+34e2)(341)= \left( \frac{3}{2} e^2 - \frac{3}{2} e^2 + \frac{3}{4} e^2 \right) - \left( \frac{3}{4} \cdot 1 \right)

=34e234= \frac{3}{4} e^2 - \frac{3}{4}

Using a calculator to approximate the values:

e27.3891e^2 \approx 7.3891

Average value=347.3891345.5418250.75=4.791825\text{Average value} = \frac{3}{4} \cdot 7.3891 - \frac{3}{4} \approx 5.541825 - 0.75 = 4.791825

Rounding to three decimal places:

Average value4.792\text{Average value} \approx 4.792

The average value of the function f(x)=3x2e2xf(x) = 3x^2 e^{2x} on the interval [0,1][0, 1] is approximately 4.792\boxed{4.792}.

Would you like more details or have any questions about this problem?

Here are five questions you can ask:

  1. How do you use integration by parts?
  2. What is the substitution method in integration?
  3. How do you find the area under a curve using definite integrals?
  4. What are the properties of the exponential function exe^x?
  5. How do you solve integrals involving polynomials and exponentials?

Tip: When dealing with integrals that combine polynomials and exponential functions, integration by parts is often a useful technique.

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Math Problem Analysis

Mathematical Concepts

Calculus
Integration
Exponential Functions

Formulas

Average value of a function over an interval
Integration by parts

Theorems

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Suitable Grade Level

Advanced Undergraduate