\(a^2-9-8ab+16b^2\)
\(=a^2-8ab+16b^2-9\)
\(=\left(a-4b\right)^2-9\)
\(=\left(a-4b-3\right)\left(a-4b+3\right)\)
a2 - 9 - 8ab + 16b2
⇔ (a2 - 8ab + 16b2) - 9
⇔ (a - 4b)2 - 32
⇔ (a - 4b - 3)(a - 4b + 3)
\(=(a^{2}-8ab+16b^{2})-9\)
\(=(a-4b)^{2}-3^{2}\)
\(=(a-4b-3)(a-4b+3)\)