The given expression is
(3x – 12)(x + 4)
We would multiply each term in the first parentheses by each term in the second as shown below
3x^2 + 12x - 12x - 48
3x^2 - 48
3 is a common factor. By factorizing, it becomes
3(x^2 - 16)
Considering the last expression,
3x(x + 4) – 12(x + 4) = 3x^2 + 12x - 12x - 48
= 3x^2 - 48
Thus, the expression that is not equivalent to (3x – 12)(x + 4) is
3(x2 – 8x + 16)