간단 한 계산 1 ⅖ (1 × 2 × 3) + 1 볘 (2 × 3 × 4) + 1 볘 (3 × 4 × 5) + 1 볘 (4 × 5 × 6) + + + 1 뽁 (98 × 99 × 100)

간단 한 계산 1 ⅖ (1 × 2 × 3) + 1 볘 (2 × 3 × 4) + 1 볘 (3 × 4 × 5) + 1 볘 (4 × 5 × 6) + + + 1 뽁 (98 × 99 × 100)

= (1 / 2) (1 / 1 × 2 - 1 / 2 × 3) + (1 / 2) (1 / 2 × 3 - 1 / 3 × 4) +...+ (1 / 2) (1 / 98 × 99 - 1 / 99 × 100)
= (1 / 2) (1 / 1 × 2 - 1 / 2 × 3 + 1 / 2 × 3 - 1 / 3 × 4 +...+ 1 / 98 × 99 - 1 / 99 × 100)
= (1 / 2) (1 / 1 × 2 - 1 / 99 × 100)
= 4949 / 19800