7. Разложите на множители многочлены: a) 225-b²; б) $$\frac{1}{16}x^2 - y^2z^2$$; в) 16a²-(3a+1)².

a) $$225 - b^2 = 15^2 - b^2 = (15-b)(15+b)$$. б) $$\frac{1}{16}x^2 - y^2z^2 = (\frac{1}{4}x)^2 - (yz)^2 = (\frac{1}{4}x - yz)(\frac{1}{4}x + yz)$$. в) $$16a^2 - (3a+1)^2 = (4a)^2 - (3a+1)^2 = (4a - (3a+1))(4a + (3a+1)) = (4a - 3a - 1)(4a + 3a + 1) = (a-1)(7a+1)$$.