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## Homework Statement

1. Determine the largest open interval where the function f(x)=2x-5/x+3 is increasing AND concave up (at the same time)

## Homework Equations

## The Attempt at a Solution

I've run through the problem and arrived at a second derivative of f''(x)= -22/(x+3)^3. Setting this to zero I'm coming back with -3. However, I keep coming back with a situation in which this is concave down. Am I making some sort of error here?