Finding area bounded Supposedly easy yet I have no clue

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    Area Bounded
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SUMMARY

The discussion focuses on approximating the area under the curve defined by the function f(x) = x² + x using the left endpoint method with four rectangles over the interval [0, 4]. Participants clarify that the area of each rectangle is calculated using the formula A = b * h, where b is the width and h is the height determined by the function value at the left endpoint. The calculated area using this method results in 88/3 or approximately 29.3333. The conversation also touches upon the right endpoint method, questioning whether the results would be the same.

PREREQUISITES
  • Understanding of basic calculus concepts, specifically Riemann sums
  • Familiarity with the function f(x) = x² + x
  • Knowledge of how to calculate the area of rectangles
  • Ability to interpret graphical representations of functions
NEXT STEPS
  • Learn about Riemann sums and their applications in calculus
  • Study the differences between left endpoint and right endpoint approximations
  • Explore the concept of limits and how they relate to finding the exact area under a curve
  • Investigate the use of definite integrals for calculating areas under curves
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Students studying calculus, educators teaching Riemann sums, and anyone interested in numerical methods for approximating areas under curves.

tjohn101
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Homework Statement


Use the left endpoint graph with the given number of
rectangles to approximate the area bounded by the
curve f (x), the x-axis, and the line x = 4.
f(x)=x2+x

Homework Equations


No idea.


The Attempt at a Solution


Once again, not a clue how to start this.
 

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tjohn101 said:

Homework Statement


Use the left endpoint graph with the given number of
rectangles to approximate the area bounded by the
curve f (x), the x-axis, and the line x = 4.
f(x)=x2+x

Homework Equations


No idea.

The Attempt at a Solution


Once again, not a clue how to start this.

Well, you are calculating the area of each rectangle, and then adding the areas up. You are using 4 rectangles from (0,4). So, you know the length of each rectangle. How do you find the height? Look at where the rectangles touch the graph (i.e., the left endpoint of the rectangle).
 
Okay, I kind of guessed my way through it based on my notes and came up with 88/3 or 29.3333_ . Now, the next question asks me to do the same thing, but use the right endpoint graph. Wouldn't the answers be the same?
 
tjohn101 said:
Okay, I kind of guessed my way through it based on my notes and came up with 88/3 or 29.3333_ . Now, the next question asks me to do the same thing, but use the right endpoint graph. Wouldn't the answers be the same?

You are splitting up the interval (0,4) like this:

(0, 1) (1, 2) (2, 3) (3, 4).

Do you see which are the left and right endpoints?
 
tjohn101 said:
Okay, I kind of guessed my way through it based on my notes and came up with 88/3 or 29.3333_ . Now, the next question asks me to do the same thing, but use the right endpoint graph. Wouldn't the answers be the same?
What did you do to calculate this? I came up with a different answer.
 
So for the left endpoints I just do A=b*h and then add them all up?

Same for the right?
 
tjohn101 said:
So for the left endpoints I just do A=b*h and then add them all up?

Same for the right?
Yep, that's really all there is to a problem of this type. You want to split up the interval, calculate the height at whichever point you're using (left, right, mid), calculate the area of each rectangle, and sum them up.

This all leads into how to calculate the REAL area under the curve, which basically has to do with splitting the interval into infinitely many rectangles!
 
Yeah that's what I'm doing now. That part's okay. Just a little long.
 

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