Real Numbers and Equality: Can x+y=4 Be Proven from x2-4x=y2-4y?

In summary, to prove that if x^2-4x=y^2-4y and x not equal to y, then x+y=4, simply move all the squared terms to one side and factor out an (x-y). This will leave you with (x+y)(x-y)=(x+y)(x-y), from which you can conclude that x+y=4.
  • #1
crakajackxx

Homework Statement



x and y are real numbers. prove that if x2-4x=y2-4y and x not equal to y, then x+y=4.

Homework Equations



n/a

The Attempt at a Solution



I tried using cases and making x and y positive and negative or even and odd, and that didnt work. then i tried completing the square on both sides and I got x=y.
please help~
 
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  • #2
Move all the terms to one side. x^2-y^2=(x+y)(x-y). Factor out an (x-y).
 
  • #3
Dick said:
Move all the terms to one side. x^2-y^2=(x+y)(x-y). Factor out an (x-y).
Dick, I think you mean "move all the squared terms to one side."
 
  • #4
Mark44 said:
Dick, I think you mean "move all the squared terms to one side."

I meant what I said. I was counting on the OP finish it from there.
 
  • #5
OK, fair enough.
 

FAQ: Real Numbers and Equality: Can x+y=4 Be Proven from x2-4x=y2-4y?

What is "proof with real numbers"?

Proof with real numbers is a method used in mathematics and science to show that a statement or hypothesis is true by providing evidence or logical reasoning using real numbers. This method is commonly used in fields such as algebra, geometry, and calculus to prove the validity of mathematical concepts and equations.

How do you conduct a proof with real numbers?

To conduct a proof with real numbers, you must first clearly state the statement or hypothesis that you are trying to prove. Then, using logical reasoning and mathematical principles, you must provide evidence that supports the statement or hypothesis using real numbers. This often involves breaking down the statement into smaller components and proving each component separately.

What are the benefits of using real numbers in a proof?

Using real numbers in a proof allows for a clear and concrete demonstration of the validity of a statement or hypothesis. It also enables the use of mathematical principles and equations to provide a logical and concise proof. Additionally, real numbers are universal and can be easily understood and verified by others.

Are there any limitations to using real numbers in a proof?

While real numbers are a powerful tool in conducting proofs, there are some limitations to their use. Real numbers are limited to representing only quantities that can be measured on a continuous scale, such as distance, time, or temperature. They cannot be used to represent discrete values, such as the number of people in a room or the number of apples in a basket.

Can a proof with real numbers be incorrect?

Yes, a proof with real numbers can be incorrect if the evidence or reasoning presented is flawed. It is important to carefully check each step of the proof and ensure that all mathematical principles and equations used are accurate. Additionally, the statement or hypothesis being proved must be clearly defined and the proof must address all possible cases and exceptions.

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