Answer:
[tex] b = 4\sqrt{2} [/tex], [tex] b = -4\sqrt{2} [/tex]
Step-by-step explanation:
For a single solution, you must have a perfect square trinomial.
[tex] -x^2 + bx - 8 = 0 [/tex]
[tex] x^2 - bx + 8 = 0 [/tex]
[tex] (x - \sqrt{8})^2 = 0 [/tex]
[tex] x^2 - 2\sqrt{8}x + 8 = 0 [/tex]
[tex] x^2 - 4\sqrt{2}x + 8 = 0 [/tex]
[tex] -x^2 + 4\sqrt{2}x - 8 = 0 [/tex]
[tex] b = \pm 4\sqrt{2} [/tex]
