- #1

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## Homework Statement

Find the smallest value of b so that the function f(x) = x^3 + 9x^2 + bx + 8 is invertible.

## Homework Equations

## The Attempt at a Solution

I know that the function has to be only increasing/decreasing, and I think it is needed to find the derivative of the function. I do however not know how b should be found.