Thread: Webwork Max and Min Values #2

#1.




#2.







I need some help finding the Max and Min of this function. As you can see I took the derivative and set it equal to zero. I know that I need the Critical Points in order to find the Max/Min, but I am wondering how I should isolate the x in order to do so. If I multiply out then I loose my x.

for #1: try 6*sqrt(37) for the max and -6*sqrt(37) for the min

I didn't work. I thought the same thing. I took the interval and plug it into f(x) and got

(-6, -36.5)

and

(6, 36.497)

This doesn't appear to be what they are looking for...

Originally Posted by qbkr21

#1.




#2.







I need some help finding the Max and Min of this function. As you can see I took the derivative and set it equal to zero. I know that I need the Critical Points in order to find the Max/Min, but I am wondering how I should isolate the x in order to do so. If I multiply out then I loose my x.

there is no solution. that function is never 0. in other words, there are no local max/min for the original function. it looks like a sqrt function. it doesn't even exist for negative x's and y's, it is only in the first quad, always increasing

Originally Posted by qbkr21

I didn't work. I thought the same thing. I took the interval and plug it into f(x) and got

(-6, -36.5)

and

(6, 36.497)

This doesn't appear to be what they are looking for...

oh? then what are they looking for, this function has no local max and min

By the way our test are 100% easier than the WebWorks problems. This can be at times a bit tricky. Also when for the first part of #2 when it says Find A: and I put in 0, zero is incorrect; thus I haven't got any credit for this problem.

Hold on a sec as I upload the actual problem. Thanks for your help. You are THEMAN!!!!

Originally Posted by qbkr21

By the way our test are 100% easier than the WebWorks problems. This can be at times a bit tricky. Also when for the first part of #2 when it says Find A: and I put in 0, zero is incorrect; thus I haven't got any credit for this problem.

i don't know what to tell you. it seems to me that in both of the questions they are asking for stuff that doesn't exists.

4(x - 5)^(2/3) has no critical point, so there is no "A"

also, the function is not defined for negative x, so asking what it is doing on (-oo, A) makes no sense

as for #1. the function has no local max or min, so i figured they want the absolute max and min, but you said that's wrong

Don't worry I appreciate your help. I will talk to Dr. Wichno tomorrow and ask him it there is a glitch in the system. I just got through dealing with one last week. I sat around for 7 hours trying to get a problem into the computer system, then I showed up Monday morning and he told us that there was a error in the latex software. This was pretty upsetting...

THIS IS WHY I HATE COMPUTER WEBWORKS. Jhevon no differentiation was involved for either of the two problems were were looking at. They wanted me to just take f(x) and set it equal to zero, not its derivative. Why would they even throw in a problem like this, when all that I have been doing for the last 2 months in computing derivatives? Hey at least we figured it out...

Originally Posted by qbkr21

Ohh... and I found out there wasn't a thing wrong with the WebWorks it was asking for the X values to the solution, thus (-6,6)