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3x4 4x5 5x6 20x21

3x4+4x5+5x6+........19x20+20x21 =3^2+3+4^2+4+...+20^2+20 =3^2+4^2+...+20^2+3+4+..+20 1^2+2^2+3^2+……+n^2=n(n+1)(2n+1)/6 1^2+2^2+...+20^2=20*21*41/6 1^2+2^2=5 所以: 3x4+4x5+5x6+........19x20+20x21 =3^2+3+4^2+4+...+20^2+20 =3^2+4...

RIPUP_ETCH FALSE; RIPUP_DELETE_FIRST_SEGMENT FALSE; RIPUP_RETAIN_BONDWIRE FALSE; RIPUP_SYMBOLS ALWAYS; Missing symbol has error FALSE; SCHEMATIC_...

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