(In reply to
What, me worry? by Steve Herman)
Some of them do look a bit complicated.
To get from the nth square to the n+1th square we need to add n units on each of two adjacent sides, plus 1 in the corner; i.e. 2n+1.
n^2+2n+1=(n+1)^2.
No need to sum series or anything like that.

Posted by broll
on 20150406 03:56:52 