(a) Establish the identity tx = ty + tz, whereand n ≥ 1, thereby proving that there are in...

(a) Establish the identity tx = ty + tz, where

and n ≥ 1, thereby proving that there are infinitely many triangular numbers that are the sum of two other such numbers.

(b) Find three examples of triangular numbers that are sums of two other triangular numbers.