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posted ago by Long_time_lurker ago by Long_time_lurker +178 / -1

We all know how terrible Marx's understanding of economics was, but how many people knew that he was a terrible mathematician, as well? Here, behold this genius trying to define 0/0:

https://www.researchgate.net/publication/255609552_Calculus_A_Marxist_approach

"In calculating the derivative of a function from first principles, Marx did not like the notion of a limit. When considering (f(x) − f(a))/(x − a) he wanted to put x = a, after suitable cancelling or some other algebraic simplification, and write the result as 0/0. He did not see 0/0 as a fraction; he saw it as one symbol."

For those who don't know, 0/0 is undefined because it literally can't have any consistent definition. So this is equivalent to starting your reasoning with a premise like x and not x, which would imply, insensibly, that everything is true.

As Wikipedia puts it, if b ≠ 0 then the equation a/b = c is equivalent to a = b × c. Assuming that a/0 is a number c, then it must be that a = 0 × c = 0. However, the single number c would then have to be determined by the equation 0 = 0 × c, but every number satisfies this equation, so we cannot assign a numerical value to 0/0.

https://en.wikipedia.org/wiki/Division_by_zero

Weird how they ... somehow forgot ... to mention that in his list of math publications, though:

https://en.wikipedia.org/wiki/Mathematical_manuscripts_of_Karl_Marx?wprov=sfla1

So if any of you are unfortunate enough to know Marx bros, you can point out that he was a terrible mathematician as well as a terrible economist.

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viking65 3 points ago +3 / -0

Not going to defend Marx, but wikipedia is not a credible source and you're basing the contradiction on an assumption that 0 = 0 x c, where c is a/0. It stands to reason that this is faulty logic, because 0 x c = a.

Division by zero can be done with a mathmatical construct, just like how the square root of negative numbers can be done by expanding into complex numbers by defining i x i = -1.

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conservativeyuppie 2 points ago +2 / -0

It stands to reason that this is faulty logic, because 0 x c = a.

If 0 x c = a, then by definition a=0.