A quadratic function can be given as follows:
[tex]f(x)=a(x-x_1)(x-x_2)[/tex]where x1 and x2 are the zeros of the equation, which means that the equation is given by:
[tex]\begin{gathered} f(x)=a(x--8)(x-4)=a(x+8)(x-4) \\ f(x)=a(x^2+4x-32) \end{gathered}[/tex]Because the point (-2, 18) is part of the function, we can substitute it, and isolate a to find its value:
[tex]\begin{gathered} a=\frac{f(x)}{x^2+4x-32}=\frac{18}{(-2)^2+4\cdot(-2)-32}=\frac{18}{4-8-32}=\frac{18}{-36}=-\frac{1}{2} \\ a=-\frac{1}{2} \end{gathered}[/tex]From the solution developed above, we are able to conclude that the answer for the present problem is:
B. -1/2