Question

Can someone explain why am I wrong and the correct answer?

Answer 1

I chose C, it is saying the answer is a

Answer 2

@Hero

Answer 3

If you could help out that would be great Hero thank you in advance!

Answer 4

First have you found \(f(x)\)? If so, is it really concave down when \(x >e\)? If so, how did you come to this conclusion?

Answer 5

@justjm

Answer 6

So my reasoning for C:

f is increasing when x>1 because when x is greater than 1, f ' (x) > 0. This means that the slope is positive so thus the function is increasing.
It is concave down because when x > e, the second derivative is negative and thus concave down.

I didn't find f(x) because I don't know integration as yet.

Answer 7

But still I gave it a try with my graphing calculator and found f(x) to be \( \frac{1}{2}ln^2x\)

And then evaluated and option C would satisfy its behavior.

Answer 8

Okay. I agree. I just wanted you to explain why you chose C.

Answer 9

Ah okay thanks. So do you think that the question was likely written wrong? It is possible and I'll give a benefit of doubt.

Answer 10

A is obviously wrong. \(f\) is clearly not decreasing on \(x > 1\)

Answer 11

Yeah of course but I'm asking if you think it graded me incorrectly and that C was right. And thanks for helping, by the way.

Answer 12

Yes, you are graded incorrectly on this one

Answer 13

Ah okay. I'll inform my teacher. Thank you

Answer 14

I don't think you really need me for this. You already found it for yourself.

Answer 15

Yeah but the question said that I got it wrong so I just needed some additional advice. So that's why I thought you were the right person to ask. But thank you once again.

Answer 16

You're welcome.