Here are some formulas for number systems: (a + b)(a – b) = (a² – b²) (a + b)² = (a² + b² + 2ab) (a – b)² = (a² + b² – 2ab) (a + b + c)² = a² + b² + c² + 2(ab + bc + ca) (a³ + b³) = (a + b)(a² – ab + b²) (a³ – b³) = (a – b)(a² + ab + b²) 1 + 2 + 3 + 4 + 5 + … + n = n(n + 1)/2 (12 + 22 + 32 + ..... + n2) = n ( n + 1 ) (2n + 1) / 6 (13+23+33+...+n3) = (1/4)n2(n+1)
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