Consider binomial \(9x^2 - 64.\)
You know that
\(9=3^2,\\ 64=8^2\)
and
\(a^2\cdot b^2=(ab)^2.\)
Then
\(9x^2 - 64=3^2\cdot x^2-8^2=(3x)^2-8^2.\)
Use formula \(a^2-b^2=(a-b)(a+b),\)
thus
\(9x^2 - 64=(3x)^2-8^2=(3x-8)(3x+8).\)
Answer: correct choice is A, 3x-8.
