Finding Limits for Triple Integrals: How to Solve for the Intersection of Planes

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Homework Help Overview

The problem involves using a triple integral to find the volume of a region defined by the inequalities below the plane x+2y+2z=4, above the plane z=2x, and constrained to the first octant.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the difficulty in determining the limits of integration for the triple integral. There are attempts to identify the y-limits and questions about finding the x and z limits. Some participants mention plotting the equations to aid in visualization.

Discussion Status

The discussion is ongoing, with participants sharing their thoughts on the intersections of the planes and their implications for setting up the integral. There is a focus on understanding the relationships between the planes and their intersections with the coordinate axes.

Contextual Notes

Participants express uncertainty about the limits of integration and the intersections of the planes, indicating a need for clarification on these aspects. There are reminders about forum posting rules regarding patience and avoiding "bumping" threads.

Timebomb3750
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Homework Statement



Use a triple integral to find the volume of the region. Below x+2y+2z=4, above z=2x, in the first octant.

Homework Equations



V=∫∫∫dV=∫∫∫dxdydz


The Attempt at a Solution



I have no clue where to begin as to finding those darn limits to integrate with. I'm sure I can evaluate the integral just fine, but I need help finding limits.
 
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Well, after plotting those two equations into my mac grapher app, it seems my y-limits could be from 0 to 2. But I'm unsure as to finding my x and z limits.
 
Any assistance would be greatly appreciated. Thanks.
 
Timebomb3750 said:
Any assistance would be greatly appreciated. Thanks.
Patience, please.

(Look at the rules for posting on this Forum, especially as regards "bumping" your thread.)
 
Timebomb3750 said:

Homework Statement



Use a triple integral to find the volume of the region. Below x+2y+2z=4, above z=2x, in the first octant.

Homework Equations



V=∫∫∫dV=∫∫∫dxdydz

The Attempt at a Solution



I have no clue where to begin as to finding those darn limits to integrate with. I'm sure I can evaluate the integral just fine, but I need help finding limits.

Timebomb3750 said:
Well, after plotting those two equations into my mac grapher app, it seems my y-limits could be from 0 to 2. But I'm unsure as to finding my x and z limits.
Where do the planes, x+2y+2z=4, and, z=2x, intersect?

Where does each of those planes intersect the coordinate axes?
 
SammyS said:
Where do the planes, x+2y+2z=4, and, z=2x, intersect?

Where does each of those planes intersect the coordinate axes?

Well, z=2x goes through the entire the y-axis, but doesn't intersect any other axes. x+2y+2z=4 intersects axes at x=4, y=2, and z=2.

The two planes intersect at 2y+5x=4.

But what's your point? What do I get out of this?
 
Timebomb3750 said:
Well, z=2x goes through the entire the y-axis, but doesn't intersect any other axes. x+2y+2z=4 intersects axes at x=4, y=2, and z=2.

The two planes intersect at 2y+5x=4.

But what's your point? What do I get out of this?
I should have asked, "Where does each of those planes intersect the coordinate planes?"

The intersection of the two planes is a line. The equation, 2y+5x=4, specifies a plane !
 

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