General Multiplication of Polynomials Examples Page 1
(3x + 4)(5x + 6)(3x - 4)
First perform the multiplication
(3x + 4)(3x - 4)
since we know this is
(9x2 - 16).
Then we can multiply the two binomials (9x2 - 16) and (5x + 6).
If instead we first multiplied (3x + 4) and (5x + 6), we would need to multiply (15x2 + 38x + 24) by (3x - 4), which would be an ugly calculation. Don't do that to yourself. You're a good person and deserve better.
Whichever way we do it, though, we should find the same final answer of