Finding Volume Using Shell Method: x=3y-y^2

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SUMMARY

The discussion focuses on calculating the volume of a solid of revolution using the shell method for the curve defined by the equation x = 3y - y², revolving around the x-axis. The volume formula V = 2π ∫ y f(y) dy is confirmed as the correct approach, where f(y) is replaced with the expression 3y - y². To determine the limits of integration, participants are advised to graph the parabola, which opens to the left, and identify the intersection points with the y-axis.

PREREQUISITES
  • Understanding of the shell method for volume calculation
  • Familiarity with the equation of a parabola
  • Ability to graph functions and identify intersection points
  • Knowledge of integral calculus, specifically definite integrals
NEXT STEPS
  • Graph the equation x = 3y - y² to identify limits of integration
  • Practice calculating volumes using the shell method with different curves
  • Explore the concept of completing the square for quadratic equations
  • Review integral calculus techniques for evaluating definite integrals
USEFUL FOR

Students studying calculus, particularly those focusing on volume calculations using the shell method, as well as educators looking for examples of integrating functions related to parabolas.

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Homework Statement



Have to find the volume using the shell method using the given curves

x=3y-y^2 and the y-axis about the x-axis

Homework Equations


I know to use the equation V=2pi Integral y f(y) dy but no idea where to get the high and low limits for the integral


The Attempt at a Solution

 
Last edited:
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Have you graphed the equation x = 3y - y^2? Its graph is a paraboloa that opens to the left. You can find the vertex of the parabola by completing the square in the y terms.

Your typical volume element is [itex]\Delta V = 2\pi*y*x*\Delta y[/itex]. Since you will be integrating with respect to y, you need to replace x in this formula with 3y - y^2. From the graph you can also get the limits of integration.
 

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