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  2. Lagrange's four-square theorem - Wikipedia

    en.wikipedia.org/wiki/Lagrange's_four-square_theorem

    In the descent above, we must rule out both the case y 1 = y 2 = y 3 = y 4 = m/2 (which would give r = m and no descent), and also the case y 1 = y 2 = y 3 = y 4 = 0 (which would give r = 0 rather than strictly positive). For both of those cases, one can check that mp = x 1 2 + x 2 2 + x 3 2 + x 4 2 would be a multiple of m 2, contradicting the ...

  3. Polyomino - Wikipedia

    en.wikipedia.org/wiki/Polyomino

    The 18 one-sided pentominoes, including 6 mirrored pairs. A polyomino is a plane geometric figure formed by joining one or more equal squares edge to edge. It is a polyform whose cells are squares. It may be regarded as a finite subset of the regular square tiling.

  4. Mental calculation - Wikipedia

    en.wikipedia.org/wiki/Mental_calculation

    The products of small numbers may be calculated by using the squares of integers; for example, to calculate 13 × 17, one can remark 15 is the mean of the two factors, and think of it as (15 − 2) × (15 + 2), i.e. 15 2 − 2 2. Knowing that 15 2 is 225 and 2 2 is 4, simple subtraction shows that 225 − 4 = 221, which is the desired product.

  5. Euler's four-square identity - Wikipedia

    en.wikipedia.org/wiki/Euler's_four-square_identity

    Comment: The proof of Euler's four-square identity is by simple algebraic evaluation. Quaternions derive from the four-square identity, which can be written as the product of two inner products of 4-dimensional vectors, yielding again an inner product of 4-dimensional vectors: (a·a)(b·b) = (a×b)·(a×b).

  6. Sums of powers - Wikipedia

    en.wikipedia.org/wiki/Sums_of_powers

    In mathematics and statistics, sums of powers occur in a number of contexts: . Sums of squares arise in many contexts. For example, in geometry, the Pythagorean theorem involves the sum of two squares; in number theory, there are Legendre's three-square theorem and Jacobi's four-square theorem; and in statistics, the analysis of variance involves summing the squares of quantities.

  7. Best CD rates for February 3, 2025 - AOL

    www.aol.com/best-cd-rates-today-outsmart...

    Editor's note: Annual percentage yields shown are as of February 3, 2025, at 8:10 a.m. ET. APYs and promotional rates for some products can vary by region and are subject to change. Sources ...

  8. Legendre's three-square theorem - Wikipedia

    en.wikipedia.org/wiki/Legendre's_three-square...

    Gauss [10] pointed out that the four squares theorem follows easily from the fact that any positive integer that is 1 or 2 mod 4 is a sum of 3 squares, because any positive integer not divisible by 4 can be reduced to this form by subtracting 0 or 1 from it. However, proving the three-square theorem is considerably more difficult than a direct ...

  9. Visa (V) Q1 2025 Earnings Call Transcript - AOL

    www.aol.com/finance/visa-v-q1-2025-earnings...

    It is moderately up from Q4, about one point, a little bit more than one point, but it still reflects a somewhat muted environment. So, it's growing at 1% in total, moving in the right direction ...