Question

Let
f(x)=(x+10)·ln(x+3)
for x>-3 . Then f(x) is concave upward on the interval (a,∞) where a =

Answer 1

For f(x) to be concave up in an interval, f''(x) > 0 in that interval.

Answer 2

I still can't find it. I found the derivative but I am still not seeing the answer.

Answer 3

Hmm what'd you get for your second derivative?
This is what I came up with:\[\Large f''(x)\quad=\quad \frac{x-4}{(x+3)^2}\]

Answer 4

Got it! Thank you!