16-x² -0.36a²+b² (c-1)²-9

16 - x^2 = 4^2 - x^2 = (4 - x)(4 + x) = - (x - 4)(x + 4) b^2 - 0.36a^2 = b^2 - (0.6a)^2 = (b - 0.6a)(b + 0.6a) (c - 1)^2 - 9 = (c - 1)^2 - 3^2 = (c - 1 - 3)(c - 1 + 3) = (c - 4)(c + 2)