What is the value of b if -x^2 + bx - 5 < 0 only when x is between (-infinity, 1) U (5, infinity)?
At the points where the curve crosses the x axis we have:
(x-1)(x-5)=0
x2-6x+5=0
multiply by -1
-x2+6x-5=0
So b = 6
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