I'm supposed to factor this completely but I don't even know where to start!
a2 ± 2ab + b2 = (a ± b)2
a2 - b2 = (a - b)(a + b)
~~~~~~~~
4a2 + 12ab + 9b2 - 25c2 = [(2a)2 + 2 · 2 · 3ab + (3b)2] - (5c)2 =
= (2a + 3b)2 - (5c)2 = (2a + 3b - 5c)(2a + 3b + 5c)