f.1數一題only!!急

A hexagonal number is a figurate number, the number of points in the union of n hexagons with partly two common sides. The hexagonal number for n is given by the formula 2 * (n^2) (that is, 2 * n * n) − n.

Therefore, all the hexagonal numbers from 50 to 120 will be:
66, 91 , and 120.

Proof:
when n is 6, 2 * (n ^ 2) - n
= 2 * 6 ^ 2 - 6
= 2 * 36 - 6
= 72 - 6
= 66
when n is 7, 2 * (n ^ 2) - n
= 2 * 7 ^ 2 - 7
= 2 * 49 - 7
= 98 - 7
= 91
when n is 8, 2 * (n ^ 2) - n
= 2 * 8 ^ 2 - 8
= 2 * 64 - 8
= 128 - 8
= 120

72,96,120
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