Math Problem Statement

Evaluate the triple integral: \( \int_0^2 \int_0^3 \int_0^{2x+y} e^{x+y+z} \, dz \, dy \, dx \).

Solution

The integral appears to be a triple integral of the form:

020302x+yex+y+zdzdydx\int_0^2 \int_0^3 \int_0^{2x+y} e^{x+y+z} \, dz \, dy \, dx

Let us evaluate this step by step:


Step 1: Evaluate the inner integral with respect to zz:

02x+yex+y+zdz\int_0^{2x+y} e^{x+y+z} \, dz

The exponential function's argument ex+y+ze^{x+y+z} is independent of zz in its partial derivative. So:

ex+y+zdz=11ex+y+z+C\int e^{x+y+z} \, dz = \frac{1}{1} e^{x+y+z} + C

Apply limits z=0z = 0 to z=2x+yz = 2x+y:

[ex+y+z]02x+y=ex+y+(2x+y)ex+y+0\left[ e^{x+y+z} \right]_0^{2x+y} = e^{x+y+(2x+y)} - e^{x+y+0}

Simplify:

e3x+2yex+ye^{3x+2y} - e^{x+y}


Step 2: Evaluate the middle integral with respect to yy:

03(e3x+2yex+y)dy\int_0^3 \left( e^{3x+2y} - e^{x+y} \right) \, dy

Split the integral:

03e3x+2ydy03ex+ydy\int_0^3 e^{3x+2y} \, dy - \int_0^3 e^{x+y} \, dy

First term:

03e3x+2ydy=e3x03e2ydy=e3x12e2y03\int_0^3 e^{3x+2y} \, dy = e^{3x} \int_0^3 e^{2y} \, dy = e^{3x} \cdot \frac{1}{2} e^{2y} \Big|_0^3

=e3x12(e61)= e^{3x} \cdot \frac{1}{2} \left( e^{6} - 1 \right)

Second term:

03ex+ydy=ex03eydy=exey03\int_0^3 e^{x+y} \, dy = e^x \int_0^3 e^y \, dy = e^x \cdot e^y \Big|_0^3

=ex(e31)= e^x \cdot \left( e^3 - 1 \right)

Thus:

03(e3x+2yex+y)dy=e3x2(e61)ex(e31)\int_0^3 \left( e^{3x+2y} - e^{x+y} \right) \, dy = \frac{e^{3x}}{2} \left( e^6 - 1 \right) - e^x \left( e^3 - 1 \right)


Step 3: Evaluate the outer integral with respect to xx:

02[e3x2(e61)ex(e31)]dx\int_0^2 \left[ \frac{e^{3x}}{2} \left( e^6 - 1 \right) - e^x \left( e^3 - 1 \right) \right] \, dx

Split into two integrals:

02e3x2(e61)dx02ex(e31)dx\int_0^2 \frac{e^{3x}}{2} \left( e^6 - 1 \right) \, dx - \int_0^2 e^x \left( e^3 - 1 \right) \, dx

First term:

02e3x2(e61)dx=(e61)202e3xdx\int_0^2 \frac{e^{3x}}{2} \left( e^6 - 1 \right) \, dx = \frac{\left( e^6 - 1 \right)}{2} \int_0^2 e^{3x} \, dx

=(e61)213e3x02= \frac{\left( e^6 - 1 \right)}{2} \cdot \frac{1}{3} e^{3x} \Big|_0^2

=(e61)6(e61)= \frac{\left( e^6 - 1 \right)}{6} \left( e^6 - 1 \right)

Second term:

02ex(e31)dx=(e31)02exdx\int_0^2 e^x \left( e^3 - 1 \right) \, dx = \left( e^3 - 1 \right) \int_0^2 e^x \, dx

=(e31)ex02= \left( e^3 - 1 \right) \cdot e^x \Big|_0^2

=(e31)(e21)= \left( e^3 - 1 \right) \left( e^2 - 1 \right)


Final Result:

Combine both terms:

020302x+yex+y+zdzdydx=(e61)26(e31)(e21)\int_0^2 \int_0^3 \int_0^{2x+y} e^{x+y+z} \, dz \, dy \, dx = \frac{\left( e^6 - 1 \right)^2}{6} - \left( e^3 - 1 \right) \left( e^2 - 1 \right)

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Math Problem Analysis

Mathematical Concepts

Triple Integration
Exponential Functions

Formulas

Integral of exponential function: \( \int e^{ax} dx = \frac{1}{a} e^{ax} + C \)
Triple integral evaluation by iterated integration

Theorems

Fundamental Theorem of Calculus

Suitable Grade Level

University level (Calculus III or Multivariable Calculus)