The function is ((x^2)-16)^6.

So I did all the relevant calculations and all my others answers about inflexion points, critical points, extreme points, concave down, increasing and decreasing intervals were correct. But my interval for concave up keeps coming up as wrong.

This is the interval I calculated:

(-INF, -4) U (-4, -((4sqrt11)/11) U ((4sqrt11))/11, 4) U (4, INF)

Does anyone know where I have went wrong here? I have been stuck on this problem for a while now.

Thank you!

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