[tex]16a -40ab+ 25a b^{2} = a(16-40b+25b^{2})[/tex]
[tex]= a(4-5b)^{2}[/tex]
[tex]b) x^{2} +8x+16 = (x + 4)^{2}[/tex]
[tex]c) (2a+3) (2a-3) = 4a^{2} - 9[/tex]
[tex]d) 7 x^{2} - y^{2} = (\sqrt{7}x-y)(\sqrt{7}x+y)[/tex]
[tex]e)x^{2} - 144 = x^{2} - 12^{2} = (x - 12)(x + 12)[/tex]