Show that the area of the rectangle is....

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    Area Rectangle
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Discussion Overview

The discussion revolves around calculating the area of a rectangle with given dimensions expressed in terms of a variable x, specifically where x is defined as $$-1\pm\sqrt{11}$$. Participants explore the implications of negative measures and the correctness of their calculations.

Discussion Character

  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant presents the dimensions of the rectangle as length $$x+1$$ and breadth $$x$$, with x being $$-1\pm\sqrt{11}$$, and asks for help in showing that the area is $$11-\sqrt{11}$$.
  • Another participant asserts that measures cannot be negative, concluding that $$x$$ must be $$\sqrt{11}-1$$, leading to the dimensions of the rectangle being $$\sqrt{11}$$ and $$\sqrt{11}-1$$.
  • Further, the same participant calculates the area as $$(-1+\sqrt{11})*(+\sqrt{11})$$ and questions the correctness of their result.
  • Several participants express confusion regarding the multiplication of the area expression by -1, questioning the rationale behind this step.

Areas of Agreement / Disagreement

Participants generally agree that measures cannot be negative, leading to a specific value for x. However, there is disagreement regarding the calculations and the interpretation of the area, as some participants challenge the multiplication by -1.

Contextual Notes

The discussion includes unresolved mathematical steps and assumptions about the validity of negative measures in the context of area calculation.

mathlearn
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There's a rectangle which the length is x+1 and the breadth is x.

X is $$-1\pm\sqrt{11}$$

Show that the area is $$11-\sqrt{11}$$

The workings I have done for far are below.

$$(-1\pm \sqrt{11})*(-1 \pm \sqrt{11} +1) $$

$$(-1\pm \sqrt{11})*( \pm \sqrt{11} ) $$

$$(-1\pm \sqrt{11})*( \pm \sqrt{11} ) $$

$$(-1\pm \sqrt{11})*( \pm \sqrt{11} ) $$

Where have I done wrong ? And the square root of the solution of the area you are asked to show is a negative. A comment here would be appreciated.

Many thanks :)
 
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Measures cannot be negative, so we must have:

$$x=\sqrt{11}-1$$

And so:

$$x+1=\sqrt{11}$$

So, what is the area?
 
MarkFL said:
Measures cannot be negative, so we must have:

$$x=\sqrt{11}-1$$

And so:

$$x+1=\sqrt{11}$$

So, what is the area?

$$(-1+ \sqrt{11})*( + \sqrt{11} ) $$

$$ - \sqrt{11}+ 11 $$

Correct? :)
 
Why would you multiply the expression representing the area by -1?

edit: I see you edited your post. :D
 
MarkFL said:
Why would you multiply the expression representing the area by -1?

edit: I see you edited your post. :D

(Party)(Party)(Happy) Thank you very much MarkFL
 

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