Proving Inequality: Using a Hint to Show (a+b)>(c+d)

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Homework Help Overview

The discussion revolves around proving the inequality a+c > b+d given the conditions a > b and c > d. The participants explore the implications of these inequalities and how to utilize a provided hint to establish the proof.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss how to apply the hint provided in the problem statement, questioning the validity of their reasoning. Some express uncertainty about their methods while attempting to connect the inequalities through algebraic manipulation.

Discussion Status

Some participants have articulated their understanding of the problem and have reached a conclusion about the proof, while others are still exploring different approaches. The conversation includes various interpretations of the hint and its application.

Contextual Notes

Participants are working under the constraints of proving the inequality without providing complete solutions, leading to a focus on reasoning and exploration of the problem's assumptions.

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Homework Statement



Prove: If a>b and c>d, then a+c>b+d
Hint: (a-b)+(c-d)=(a+c)-(b+d)>0

Homework Equations





The Attempt at a Solution



How to use the hint to prove the inequality?
My method, not sure it's right.
Given c>d, c-d>0
Given a>b => a+(c-d)>b
Thus a+c>b+d
 
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azizlwl said:

Homework Statement



Prove: If a>b and c>d, then a+c>b+d
Hint: (a-b)+(c-d)=(a+c)-(b+d)>0

Homework Equations





The Attempt at a Solution



How to use the hint to prove the inequality?
My method, not sure it's right.
Given c>d, c-d>0
right.
azizlwl said:
Given a>b => a+(c-d)>b
Why not continue with the same line of thinking as above?

a > b implies what about a - b?
azizlwl said:
Thus a+c>b+d
 


ok i see it now

Given a>b =>a-b>0
Given c>d =>c-d>0

(a-b)+(c-d)>0
(a+c)-(b+d)>0
thus a+c>b+d

thank you
 


Another way to do this, and, in my opinion, simpler, is this:
Since a> b, a+ c> b+ c.
Since c> d, b+ c> b+ d.
Since ">" is transitive a+ c> b+ d.
 

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