a) (81 - 4a^2 = (9 + 2a)(9 - 2a))
b) (25m^2 - 10mn + n^2 = (5m - n)^2)
c) (16c^2 + 8c + 1 = (4c + 1)^2)
a) (81 - 4a^2 = (9 + 2a)(9 - 2a))
b) (25m^2 - 10mn + n^2 = (5m - n)^2)
c) (16c^2 + 8c + 1 = (4c + 1)^2)