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  2. Collatz conjecture - Wikipedia

    en.wikipedia.org/wiki/Collatz_conjecture

    If a term is odd, the next term is 3 times the previous term plus 1. The conjecture is that these sequences always reach 1, no matter which positive integer is chosen to start the sequence. The conjecture has been shown to hold for all positive integers up to 2.95 × 10 20, but no general proof has been found.

  3. Proof of impossibility - Wikipedia

    en.wikipedia.org/wiki/Proof_of_impossibility

    One of the widely used types of impossibility proof is proof by contradiction.In this type of proof, it is shown that if a proposition, such as a solution to a particular class of equations, is assumed to hold, then via deduction two mutually contradictory things can be shown to hold, such as a number being both even and odd or both negative and positive.

  4. Proving a negative - Wikipedia

    en.wikipedia.org/wiki/Proving_a_negative

    Proving a negative or negative proof may refer to: Proving a negative, in the philosophic burden of proof; Evidence of absence in general, such as evidence that there is no milk in a certain bowl; Modus tollens, a logical proof; Proof of impossibility, mathematics; Russell's teapot, an analogy: inability to disprove does not prove

  5. Scientists find evidence of ‘negative time’ - AOL

    www.aol.com/news/scientists-evidence-negative...

    Scientists claim to have found evidence of “negative time” after observing photons exiting a material before entering it. A team of quantum physicists from the University of Toronto in Canada ...

  6. Negative number - Wikipedia

    en.wikipedia.org/wiki/Negative_number

    the product of a negative number—al-nāqiṣ (loss)—by a positive number—al-zāʾid (gain)—is negative, and by a negative number is positive. If we subtract a negative number from a higher negative number, the remainder is their negative difference. The difference remains positive if we subtract a negative number from a lower negative ...

  7. Descartes' rule of signs - Wikipedia

    en.wikipedia.org/wiki/Descartes'_rule_of_signs

    The number of positive real roots is at most the number of sign changes in the sequence of polynomial's coefficients (omitting zero coefficients), and the difference between the root count and the sign change count is always even. In particular, when the number of sign changes is zero or one, then there are exactly zero or one positive roots.

  8. Divisibility rule - Wikipedia

    en.wikipedia.org/wiki/Divisibility_rule

    Subtracting 9 times the last digit from the rest gives a multiple of 7. (Works because (90 + 1) is divisible by 7.) 483: 48 − (3 × 9) = 21 = 7 × 3. Adding 3 times the first digit to the next and then writing the rest gives a multiple of 7. (This works because 10a + b − 7a = 3a + b; the last number has the same remainder as 10a + b.)

  9. Lottery winner ‘shocked’ after using calculator 5 times to ...

    www.aol.com/lottery-winner-shocked-using...

    “I got my calculator out and calculated it five times,” he said. The $50,000 prize is one of 50 offered in the game, which has a top reward of $5 million. Man couldn’t find his lottery ticket.