= 2 * ( (n-2) + (n-1) + n +... + (2n-5) )
...
I don't understand where the (2n-5) comes from in line 2, and then why we use it in the summation on line 3. Nor do I understand where those summations come from on line 3 and why we subtract them.
= 2 * ( (n-2) + (n-1) + n +... + (2n-5) )
...
I don't understand where the (2n-5) comes from in line 2, and then why we use it in the summation on line 3. Nor do I understand where those summations come from on line 3 and why we subtract them.