What is the value of b + c if x^2 + bx + c > 0 only when x is in (-inf,2) U (8,inf)?
The domain shows this to be a dome shaped parabola with zeroes ( roots ) at 2 and 8
the quadratic then becomes
( x-2)(x-8) expand
x^2 -10x + 16 >0 <======== take it from here
Here is a graph : https://www.desmos.com/calculator/7f05zasszq