Yay! More Calculus problems!


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Neowin probably isn't the best place to get help with Calculus but until I find a better site, fellow Neowinians get to be mathematicians!

This is Calculus from the Saxon Math Series.

let f(x) = x(x-2)(x+4)(x-6) which of the following is true?

a.f is positive over the interval (-4,0)

b. f is negative over the interval (-infinity, -4)

c. f has a root at x=3

d. f is positive over the interval (0,2)

Next problem.

a. write log (2exponent 3 multiplied by 7 exponent 5) in terms of log 2 and log 7.

b. write ln x exponent 4 divided by y exponent 8 in terms of ln x and ln y.

Thanks!

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First problem, answer is (d)

The other two are very easy....give them a try and discuss the answers here.

EDIT: I just wanted to know, where does Calculus come into these problems? They seem to be oral type.

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doesn't seem like you are trying, you don't even have to know anything about math or mathematical functions, you can find the answers by trial and error within a minute

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He he he, I will explain guys. Our math teacher (who teaches us calculus) had heart surgery this last summer. Because of that, a normally excellent teacher has been reduced to talking sightly above a whisper and his writing is unreadable, but the school won't do anything about it.

So for our class this year, most of the lessons had to be self taught. You guys were yelling at me for putting 2 problems up there, yet I didn't list the other 23 I completed in the lesson.

.Ark: Thanks for the opinion, but take up your argument with Saxon Math.

I should have explained what I knew about those problems.

The first one, I know how you graph it with the opposite of the points so 2,-4,6 and draw a curvy line after you input whatever value you want into the x. I just needed to double check my answer on that one.

The second problem I listed, are normally very easy. This less they put it backwards and with a twist, hence why I asked.

Sorry I didn't include any work or explanation about what I know, so I'll forgive the "your not even trying" comments.

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Well the log one wasn't like the normal ones because it had 2 different variables of which we were not used too. If it said x exponent 4 and x exponent 8 then I would know how to do it. I'll try anyways...

ln sub x multiplied by y with 4 multiplied by 8 on the end? Arggg, the double variables is killing me.

Got the curve one so that is no issue.

One last one though that I think I need to look at again.

what is the domain of f(x) = 2ln(x+2)?

the answer is either x is greater than or equal to -2 or just greater than -2. I am questioning this one because I couldn't remember if having a 0 in the () mattered since you have a 2 by the ln.

Finally is the answer to one of those log problems, log sub 2 then 3 and log sub 7 then 5?

For 15+ lessons the log ones have always been simpler so without a new lesson talking about the 2nd variable, I was a bit lost.

Here is a picture for the log problems if that helps.

calculushelpfz6.th.jpg

Edited by mystic54
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Think of it like this:

ln0=x (say)

=>0=e^x, which is not possible. Therefore, ln0 is meaningless, ie, 0 is not in the domain. Therefore, x>-2.

Ah that makes so much more sense, thanks!

I guess I will just wing it on that log problem and hope it goes well because I still never figured it out last night.

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Sorry to double post, but we got the day off in math today (too many students gone). So, I have one more day to figure out that log problem before I go to bed, but I am still where I am yesterday, stuck because it has 2 variables instead of the usual one.

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