Q: How do I factor this: 27 – 64x6
A: This looks like a difference of cubes… How do I know? It looks like (something cubed) – (something else cubed).
The difference of cubes formula is one you have to memorize or just have handy… It says:
a3 – b3 = (a – b)(a2 + ab + b2)
[I color-coded it to make it easier for the next steps].
OK, back to our original problem… I need to make it look like (something)3 – (something)3
27 – 64x6 = 3³ – (4x2)³
So, we have:
3³ – (4x2)³ = (3 – 4x2)(32 + 3*4x2 + (4x2)2)
Now, simplify the right side:
(3 – 4x2)(32 + 3*4x2 + (4x2)2) = (3 – 4x2)(9 + 12x2 + 16x4)
There it is!