# check my answers plz

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• Feb 28th 2009, 02:04 PM
jkami
check my answers plz
Find the local extreme points, concavity and inflecton points using first and second derivative test.

1. $\displaystyle h(x)=xlnx$

My answer: Local Minimim (0.37, -0.37), concave up, no infection points

2. $\displaystyle g(x)=\frac1{t}$

My answer: no extreme points, no concavity, no inflection points

3. $\displaystyle m(x)=2x+\frac1{x}$

My answer:
Local Maxium$\displaystyle (-\frac{1}{\sqrt2}, -2-\frac2{\sqrt2})$ concave down
Local Minimum$\displaystyle (\frac{1}{\sqrt2}, 2+\frac2{\sqrt2})$ concave up
No inflection points

4. $\displaystyle w(x)=x^4-2x^2+x+1$

My answer: no extreme points, no concavity, no inflection points

5.$\displaystyle w(s)=s^2e^s$

My answer:
Local Minimum$\displaystyle (0,0)$ concave down
Local Maximum$\displaystyle (-2,\frac1{2})$ concave up
No inflection points
• Feb 28th 2009, 02:19 PM
mr fantastic
Quote:

Originally Posted by jkami
Find the local extreme points, concavity and inflecton points using first and second derivative test.

1. $\displaystyle h(x)=xlnx$

My answer: Local Minimim (0.37, -0.37), concave up, no infection points

2. $\displaystyle g(x)=\frac1{t}$

My answer: no extreme points, no concavity, no inflection points

3. $\displaystyle m(x)=2x+\frac1{x}$

My answer:
Local Maxium$\displaystyle (-\frac{1}{\sqrt2}, -2-\frac2{\sqrt2})$ concave down
Local Minimum$\displaystyle (\frac{1}{\sqrt2}, 2+\frac2{\sqrt2})$ concave up
No inflection points

4. $\displaystyle w(x)=x^4-2x^2+x+1$

My answer: no extreme points, no concavity, no inflection points

5.$\displaystyle w(s)=s^2e^s$

My answer:
Local Minimum$\displaystyle (0,0)$ concave down
Local Maximum$\displaystyle (-2,\frac1{2})$ concave up
No inflection points

Don't you have answers to check against?

(If these are questions from a graded task, then it's not appropriate to be asking us to check your answers).
• Feb 28th 2009, 04:21 PM
jkami
What is your problem? I am here to receive help! If you don't know how to do these problems, you don't have to reply. In fact, I tried my best to do all these problems and I just want to know whether I did it correctly or not. I am not asking you to give me the correct answer, you only have to tell me which question I did was wrong, so I can do it again until I get it right.
• Feb 28th 2009, 06:06 PM
mr fantastic
Quote:

Originally Posted by jkami
What is your problem? I am here to receive help! If you don't know how to do these problems, you don't have to reply. In fact, I tried my best to do all these problems and I just want to know whether I did it correctly or not. I am not asking you to give me the correct answer, you only have to tell me which question I did was wrong, so I can do it again until I get it right.

My problem is that it takes time and effort to check answers. That's why I asked if you have access to answers. If these are practise questions then surely it is the responsibility of your teacher to provide you with this.

And if you want these answers checked because the questions are part of a graded assessment that you are handing in, then I thought I'd do you the courtesy of letting you know what MHF policy is on that.

If you post your working, together with your answer, it will take much less effort and time (things that you are getting for free I might add) to check what you've done.

So if you would care to answer the question I asked ......

By the way, all the questions I have asked at all your threads have been designed to help you answer the questions yourself rather than spoon feeding you the solution. Your replies have suggested that you could actually do most of them ....