Question 1143563
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(2(2-1))/2 = 2/2 = 1
(3(3-1))/2 = 6/2 = 3
(4(4-1))/2 = 12/2 = 6
(5(5-1))/2 = 20/2 = 10<br>
The rule is<br>
(n(n-1))/2