Answer:
b = -2
Explanation:
Take the cube root of both sides of the equation.
b^3 = (-2)^3
b = -2
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There are two other complex solutions. It isn't clear from the problem statement whether you are interested in those or not. They are 1±i√3. They can be found by factoring b^3+8 = 0 as (b+2)(b^2 -2b +4) = 0. They are the roots of the quadratic.