Answer:
450·a^2 + 242·c^2 + 660·a·c
= 2·(225·a^2 + 330·a·c + 121·c^2)
= 2·((15·a)^2 + 2·(15·a)·(11·c) + (11·c)^2)
= 2·(15·a + 11·c)^2
