A strange fact as well as big doubt

In summary, the issue with trying to take the derivative of f(x) = x+x+x... (x times) is that the function is not continuous and the way "x times" is defined is unclear. This results in a faulty derivative and the apparent contradiction of 1=2.
  • #1
iitjee10
57
0
We know x^2 = x*x*x*x... x times
If we differentiate both sides with respect to x, we have
2x=1+1+1+... x times
i.e. 2x=x
i.e 1=2
How is it possible or am i making a mistake?

Please helpp!
 
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  • #2
iitjee10 said:
We know x^2 = x*x*x*x... x times
If we differentiate both sides with respect to x, we have
2x=1+1+1+... x times
i.e. 2x=x
i.e 1=2
How is it possible or am i making a mistake?

Please helpp!
Erm, well to start with x2 = x*x
 
  • #3
I'm assuming you meant x+x+x+x... x times.

The problem with trying to take the derivative of that with respect to x is first, the number of terms changes as well as each term itself, and second, you can't really write it like that if x is not a nonnegative integer.
 
  • #4
And even if x is a nonnegative integer, your function, f(x) = x+x+x... (x times), is only defined at the nonnegative integers, so your function f(x) isn't continuous anywhere, so it can't be differentiated.
 
  • #5
Your way of handling addition and multiplication is confused as you have not prperly defined what x times means. That aside the problem with your differentiation is that for a derivative to be correct all x in the function must be allowed to vary, you hold your x times fixed.
x^2=x+x+x+... xtimes
differentiate
2x=x'+x'+x'+... xtimes
+x+x+x+... x' times
=1+1+1+... x times
+x+x+x+... 1 times
=x+x=2x

So the problems were holding the x in "x times" fixed and not properly defining what "x times means.
 
  • #6
lurflurf said:
Your way of handling addition and multiplication is confused as you have not prperly defined what x times means. That aside the problem with your differentiation is that for a derivative to be correct all x in the function must be allowed to vary, you hold your x times fixed.
x^2=x+x+x+... xtimes
differentiate
2x=x'+x'+x'+... xtimes
+x+x+x+... x' times
=1+1+1+... x times
+x+x+x+... 1 times
=x+x=2x

So the problems were holding the x in "x times" fixed and not properly defining what "x times means.

Very interesting actually. I had never thought of that.
 

FAQ: A strange fact as well as big doubt

What is the strange fact being referred to?

The strange fact being referred to is a piece of information or phenomenon that is unexpected, unusual, or difficult to explain.

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A strange fact is different from a regular fact because it often goes against common knowledge or beliefs and may seem unbelievable or surprising.

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A big doubt refers to the skepticism or uncertainty surrounding a strange fact. It could be a question of validity, reliability, or plausibility.

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As scientists, it is important to pay attention to strange facts and big doubts because they challenge our current understanding and can lead to new discoveries and advancements in our fields. They also encourage critical thinking and questioning of established ideas.

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