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. Evaluate the following definite integrals:a) ∫ (𝑒2𝑥 + 𝑒𝑥)𝑑𝑥32 (3)b) ∫ ( 1𝑥+2)𝑒−2−1 𝑑𝑥

Question

Evaluate the following definite integrals:

a) ∫ (𝑒^{2𝑥} + 𝑒^{𝑥})𝑑𝑥 from 3 to 2
b) ∫ (\frac{1}{𝑥+2})𝑒^{−2} from -1 to ( \

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Solution

1. Break Down the Problem

We have two definite integrals to evaluate: a) 23(e2x+ex)dx \int_{2}^{3} (e^{2x} + e^{x}) \, dx
b) 12(1x+2)e2dx \int_{-1}^{-2} \left(\frac{1}{x+2}\right) e^{-2} \, dx

2. Relevant Concepts

For both integrals, we need to find the antiderivative and then evaluate it at the given limits.

a) The integral of (e2x+ex) (e^{2x} + e^{x}) can be broken down as:
(e2x+ex)dx=e2xdx+exdx \int (e^{2x} + e^{x}) \, dx = \int e^{2x} \, dx + \int e^{x} \, dx

b) The integral of 1x+2e2 \frac{1}{x+2} e^{-2} can be simplified since e2 e^{-2} is a constant multiplier. So: (1x+2)e2dx=e21x+2dx \int \left(\frac{1}{x+2}\right) e^{-2} \, dx = e^{-2} \int \frac{1}{x+2} \, dx

3. Analysis and Detail

a) Compute 23(e2x+ex)dx \int_{2}^{3} (e^{2x} + e^{x}) \, dx

  1. Find the antiderivative:
    e2xdx=12e2x+C \int e^{2x} \, dx = \frac{1}{2} e^{2x} + C
    exdx=ex+C \int e^{x} \, dx = e^{x} + C
    Combine:
    (e2x+ex)dx=12e2x+ex+C \int (e^{2x} + e^{x}) \, dx = \frac{1}{2} e^{2x} + e^{x} + C

  2. Evaluate from 2 to 3:
    F(3)=12e6+e3 F(3) = \frac{1}{2} e^{6} + e^{3}
    F(2)=12e4+e2 F(2) = \frac{1}{2} e^{4} + e^{2}
    Thus,
    23(e2x+ex)dx=F(3)F(2)=(12e6+e3)(12e4+e2) \int_{2}^{3} (e^{2x} + e^{x}) \, dx = F(3) - F(2) = \left( \frac{1}{2} e^{6} + e^{3} \right) - \left( \frac{1}{2} e^{4} + e^{2} \right)

b) Compute 12(1x+2)e2dx \int_{-1}^{-2} \left(\frac{1}{x+2}\right) e^{-2} \, dx

  1. Find the antiderivative: 1x+2dx=lnx+2+C \int \frac{1}{x+2} \, dx = \ln|x+2| + C

  2. Evaluate from -1 to -2 (note the limits are reversed so we will flip the sign): F(1)=ln1=0 F(-1) = \ln|1| = 0
    F(2)=ln0 (undefined, hence cannot evaluate directly) F(-2) = \ln|0| \text{ (undefined, hence cannot evaluate directly)}

4. Verify and Summarize

For b) b) , because F(2) F(-2) is not defined (as ln(0) \ln(0) is undefined), we note that the integral does not yield a well-defined value.

Final Answer

a) The final result for the first integral is:
23(e2x+ex)dx=12e6+e312e4e2 \int_{2}^{3} (e^{2x} + e^{x}) \, dx = \frac{1}{2} e^{6} + e^{3} - \frac{1}{2} e^{4} - e^{2}

b) The integral 12(1x+2)e2dx \int_{-1}^{-2} \left(\frac{1}{x+2}\right) e^{-2} \, dx is undefined due to the logarithmic singularity at x=2 x = -2 .

This problem has been solved

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