What is 1.25 times 2 / 3 times 0.8? What is 1 / 2 plus 1 / 3 times 1 / 2 plus 1 / 3?

2/3,1

The square of 2 minus the square of 0 equals 4 equals 1 * 4; the square of 4 minus the square of 2 equals 12 equals 3 * 4; the square of 6 minus the square of 4 equals 4
20 equals 5 * 4, 8 minus 6 equals 28 equals 7 * 4... What do you find? Please use letters to express numbers and write down the rules you find

n²－（n－2）²＝（n－1）﹡4

1＋2＋3＋4＋5＋6…… How much is + 10000,

Summation formula of arithmetic sequence (first term + last term) * number of terms / 2 (1 + 10000) * 10000 / 2 = 50005000

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