(1+2+3)+(2+3+4)+(3+4+5)+……(498+499+500)=?谁能告示
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(1+2+3)+(2+3+4)+(3+4+5)+……(498+499+500)=?谁能告示
(1+2+3)+(2+3+4)+(3+4+5)+……(498+499+500)=?
谁能告示
(1+2+3)+(2+3+4)+(3+4+5)+……(498+499+500)=?谁能告示
(1+2+3)+(2+3+4)+(3+4+5)+……(498+499+500)
= 1 + 2 * 2 + 3 * 3 + 4 * 3 + 5 * 3 + ... + 498 * 3 + 499 * 2 + 500
= (1 + 2 + 3 + ... + 499) * 3 - 1 * 2 - 2 * 1 - 499 * 1 + 500
= (1 + 499) * 499 / 2 * 3 - 2 - 2 + 1
= 250 * 499 * 3 - 3
= 374250 - 3
= 374247
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