I'm given f''(x) = sin(3x)ln(x+5) - xcos(3x)

1. List intervals where f(x) concave up & concave down with justification.

Normally you can find this by getting f''(x) = 0 right? But how do I take that function = 0?

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- Nov 6th 2012, 11:27 PMmettlerSecond Derivative Interpretation
I'm given f''(x) = sin(3x)ln(x+5) - xcos(3x)

1. List intervals where f(x) concave up & concave down with justification.

Normally you can find this by getting f''(x) = 0 right? But how do I take that function = 0? - Nov 7th 2012, 06:27 AMSorobanRe: Second Derivative Interpretation
Hello, mettler!

I've made a few observations . . . that's all.

Quote:

I'm given:

1. List intervals where is concave up & concave down with justification.

Normally you can find this by getting , right?

But how do I take that function = 0?

Note that the domain is

The equation cannot be solved by elementary means.

By inspection, we find that is a solution.