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