What was the longest-standing incorrect proof of the Four Color Theorem in graph theory?
The longest-standing incorrect proof of the Four Color Theorem in graph theory was produced by Kempe in 1879. He claimed to have proved the theorem using a technique known as “reduction to absurdity”, which involved coloring maps and deriving a contradiction when certain conditions were not met. However, this proof was later discovered to be flawed and was soon corrected by other mathematicians. It took over a century of work by many mathematicians to finally prove the Four Color Theorem rigorously, with the first correct proof being published in 1976.
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### Instruction:

What was the longest-standing incorrect proof of the Four Color Theorem in graph theory?

### Response:

The longest-standing incorrect proof of the Four Color Theorem in graph theory was produced by Kempe in 1879. He claimed to have proved the theorem using a technique known as “reduction to absurdity”, which involved coloring maps and deriving a contradiction when certain conditions were not met. However, this proof was later discovered to be flawed and was soon corrected by other mathematicians. It took over a century of work by many mathematicians to finally prove the Four Color Theorem rigorously, with the first correct proof being published in 1976.
