Question 400064
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Hi
f(x) = x^2 + ax + 15 with a minimum value of -12
f(x) = (x+ a/2)^2 - a^2/4 + 15
Using the vertex form of a parabola, {{{y=a(x-h)^2 +k}}} where(h,k) is the vertex
 -a^2/4 + 15 = -12
      27 = a^2/4
      27*4 = a^2
        a = ± sqrt(108)