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  2. Four color theorem - Wikipedia

    en.wikipedia.org/wiki/Four_color_theorem

    Initially, this proof was not accepted by all mathematicians because the computer-assisted proof was infeasible for a human to check by hand. [2] The proof has gained wide acceptance since then, although some doubts remain. [3] The theorem is a stronger version of the five color theorem, which can be shown using a significantly simpler argument.

  3. MacMahon Squares - Wikipedia

    en.wikipedia.org/wiki/MacMahon_Squares

    The goal is to arrange the squares into a 4 by 6 grid so that when two squares share an edge, the common edge is the same color in both squares. In 1964, a supercomputer was used to produce 12,261 solutions to the basic version of the MacMahon Squares puzzle, with a runtime of about 40 hours. [2]

  4. Rook polynomial - Wikipedia

    en.wikipedia.org/wiki/Rook_polynomial

    The number of arrangements for a (4n + 1) × (4n + 1) board is the same as that for a 4n × 4n board; this is because on a (4n + 1) × (4n + 1) board, one rook must necessarily stand in the centre and thus the central rank and file can be removed. Therefore R 4n + 1 = R 4n. For the traditional chessboard (n = 2), R 8 = 4 × 3 × 1 = 12 possible ...

  5. Graph coloring - Wikipedia

    en.wikipedia.org/wiki/Graph_coloring

    With only two colors, it cannot be colored at all. With four colors, it can be colored in 24 + 4 × 12 = 72 ways: using all four colors, there are 4! = 24 valid colorings (every assignment of four colors to any 4-vertex graph is a proper coloring); and for every choice of three of the four colors, there are 12 valid 3-colorings. So, for the ...

  6. Casus irreducibilis - Wikipedia

    en.wikipedia.org/wiki/Casus_irreducibilis

    Casus irreducibilis occurs when none of the roots are rational and when all three roots are distinct and real; the case of three distinct real roots occurs if and only if ⁠ q 2 / 4 ⁠ + ⁠ p 3 / 27 ⁠ < 0, in which case Cardano's formula involves first taking the square root of a negative number, which is imaginary, and then taking the ...

  7. Completing the square - Wikipedia

    en.wikipedia.org/wiki/Completing_the_square

    In contrast, the graph of the function f(x) + k = x 2 + k is a parabola shifted upward by k whose vertex is at (0, k), as shown in the center figure. Combining both horizontal and vertical shifts yields f(x − h) + k = (x − h) 2 + k is a parabola shifted to the right by h and upward by k whose vertex is at (h, k), as shown in the bottom figure.

  8. AOL Mail

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  9. Mathematical chess problem - Wikipedia

    en.wikipedia.org/wiki/Mathematical_chess_problem

    A mathematical chess problem is a mathematical problem which is formulated using a chessboard and chess pieces. These problems belong to recreational mathematics.The most well-known problems of this kind are the eight queens puzzle and the knight's tour problem, which have connection to graph theory and combinatorics.