In an equation of the form $k = ax^2 + bx + c$ with $a > 0$, the least possible value of $k$ occurs at $x = -b/(2a)$. In the equation $k = (6x + 12)(x - 8)$, what is the least possible value for $k$?

Thank you in advance, and sorry if this question was already posted before.

JocelynSun May 16, 2022