AMC 12A 2005 Problem 9

Past Contests AMC 12 AMC 12A - 2005
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1

There are two values of a for which the equation 4 x^{2}+a x+8 x+9=0 has only one solution for x. What is the sum of those values of a ?

Answer Choices
A. -16
B. -8
C. 0
D. 8
E. 20