To find the average value of the function f(x)=3x2e2x on the interval [0,1], we use the formula for the average value of a function f over the interval [a,b]:
Average value=b−a1∫abf(x)dx
In this case, a=0 and b=1. Thus, we have:
Average value=1−01∫013x2e2xdx=∫013x2e2xdx
To solve this integral, we will use integration by parts. Let u=x2 and dv=3e2xdx. Then, we have du=2xdx and v=23e2x.
Using integration by parts formula ∫udv=uv−∫vdu:
∫3x2e2xdx=(x2⋅23e2x)−∫(23e2x⋅2x)dx
=23x2e2x−3∫xe2xdx
Now, we need to integrate xe2x. Again, we use integration by parts. Let u=x and dv=e2xdx. Then, du=dx and v=21e2x:
∫xe2xdx=(x⋅21e2x)−∫(21e2x⋅1)dx
=21xe2x−21∫e2xdx
=21xe2x−21⋅21e2x=21xe2x−41e2x
Putting it all together:
∫3x2e2xdx=23x2e2x−3(21xe2x−41e2x)
=23x2e2x−23xe2x+43e2x
Now, we evaluate this expression from 0 to 1:
[23x2e2x−23xe2x+43e2x]01
=(23⋅12⋅e2⋅1−23⋅1⋅e2⋅1+43e2⋅1)−(23⋅02⋅e2⋅0−23⋅0⋅e2⋅0+43e2⋅0)
=(23e2−23e2+43e2)−(43⋅1)
=43e2−43
Using a calculator to approximate the values:
e2≈7.3891
Average value=43⋅7.3891−43≈5.541825−0.75=4.791825
Rounding to three decimal places:
Average value≈4.792
The average value of the function f(x)=3x2e2x on the interval [0,1] is approximately 4.792.
Would you like more details or have any questions about this problem?
Here are five questions you can ask:
- How do you use integration by parts?
- What is the substitution method in integration?
- How do you find the area under a curve using definite integrals?
- What are the properties of the exponential function ex?
- 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.