Time Complexity using recurrence method

#1

We have to do the sum from 1 to n.
Then why sir writes it n(n-1)/2.
Because it will contradict the previous video in which sir says that O(n^2) means the complexity will never cross the values n^2.

#2

@a19JE0093
hello akshat ,
complexity equal to O(n^2) means complexity will never cross k*n^2 where k is some arbitrary constant.

#3

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