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

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In summary, proving an inequality means using mathematical reasoning to demonstrate that one side of the inequality is always greater or less than the other. It is important because it allows us to compare and contrast quantities and make conclusions about their relationships. Common techniques used include mathematical induction, contradiction, and algebraic and geometric manipulations. To determine if an inequality is true or false, you can use methods such as plugging in values, graphing, or using mathematical proofs. Real-world applications of proving inequalities include optimizing processes, analyzing investments, and determining stability in physical systems. It is also used in fields such as engineering, economics, and computer science.
  • #1
azizlwl
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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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  • #2


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
 
  • #3


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
 
  • #5


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.
 

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

What does it mean to "prove an inequality"?

Proving an inequality means showing that the statement is true for all possible values of the variables involved. It involves using mathematical reasoning and logic to demonstrate that one side of the inequality is always greater than or less than the other side.

Why is proving inequalities important?

Proving inequalities is important because it allows us to compare and contrast different quantities and make conclusions about their relationships. This is especially useful in fields such as economics, physics, and statistics.

What are some common techniques used to prove inequalities?

Some common techniques used to prove inequalities include mathematical induction, the method of contradiction, and the use of algebraic and geometric manipulations. Other methods such as the Cauchy-Schwarz inequality and the AM-GM inequality are also commonly used.

How do you know if an inequality is true or false?

To determine if an inequality is true or false, you can use various methods such as plugging in values for the variables, graphing the inequality, or using mathematical proofs. In some cases, you may also need to use numerical or computational methods to verify the inequality.

What are some real-world applications of proving inequalities?

Proving inequalities has many real-world applications, such as in optimizing production processes, analyzing financial investments, and determining the stability of physical systems. It is also commonly used in fields such as engineering, economics, and computer science.

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