# I need help in Calculus (Need Consensus Fast)

**URL:** <https://boards.straightdope.com/t/i-need-help-in-calculus-need-consensus-fast/627950>\
**Category:** Factual Questions\
**Created:** [July 12, 2012, 1:28am UTC](https://boards.straightdope.com/t/i-need-help-in-calculus-need-consensus-fast/627950 "2012-07-12T01:28:12Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![Sue\_Duhnym](https://avatars.discourse-cdn.com/v4/letter/s/91b2a8/32.png) [@Sue\_Duhnym](https://boards.straightdope.com/u/Sue_Duhnym)\
**Post date:** [July 12, 2012, 1:28am UTC](https://boards.straightdope.com/t/i-need-help-in-calculus-need-consensus-fast/627950/1 "2012-07-12T01:28:12Z")

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I’m taking Calc1 over the summer which, as a 5-credit class, is particularly brutal. I’m in class 14 hours/week and doing at least twice that in homework plus a husband and kids. Let’s not talk about how insane I am, please.

Here’s the issue: I got an 82% on my first test. My second, 65% (I’ve had straight As thus far, so this is killing me). The prof allows us to “fix” one test for half of the remaining points so if I get everything correct on this fix, I can bring it up to an 82, which is huge.

I’ve finished every other error but, I’m stuck on one problem and I need some help. It’s regarding the chain rule of derivatives. Here is the problem:

Let f, g and h be differentiable functions. Find:

[f ° g (x) + x^3h^2(x)]

My answer is currently this:

[fʹg(x) \* gʹ(x)] + [3x^2h^2(x) \* x^32h(x) \* hʹ(x)]

Is that even close to correct? Please help!

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**Author:** ![Thudlow\_Boink](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/thudlow_boink/32/320_2.png) [@Thudlow\_Boink](https://boards.straightdope.com/u/Thudlow_Boink)\
**Post date:** [July 12, 2012, 1:41am UTC](https://boards.straightdope.com/t/i-need-help-in-calculus-need-consensus-fast/627950/2 "2012-07-12T01:41:14Z")

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At the risk of running afoul of the “no help on homework” rule: yes, it looks correct (assuming I understand your notation correctly).

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**Author:** ![Sue\_Duhnym](https://avatars.discourse-cdn.com/v4/letter/s/91b2a8/32.png) [@Sue\_Duhnym](https://boards.straightdope.com/u/Sue_Duhnym)\
**Post date:** [July 12, 2012, 1:48am UTC](https://boards.straightdope.com/t/i-need-help-in-calculus-need-consensus-fast/627950/3 "2012-07-12T01:48:15Z")

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> [@Thudlow\_Boink](#):
>
> At the risk of running afoul of the “no help on homework” rule: yes, it looks correct (assuming I understand your notation correctly).

There’s a “no homework” rule? Well, shit. Sorry mods. Feel free to close this if I’ve violated it. I apologize.

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**Author:** ![Topologist](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/topologist/32/3208_2.png) [@Topologist](https://boards.straightdope.com/u/Topologist)\
**Post date:** [July 12, 2012, 1:50am UTC](https://boards.straightdope.com/t/i-need-help-in-calculus-need-consensus-fast/627950/4 "2012-07-12T01:50:09Z")

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There’s one mistake I see. I’ll just point out that you should be using the product rule on x[sup]3[/sup]h[sup]2/sup and you’ve made a mistake in doing so.

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**Author:** ![Simplicio](https://avatars.discourse-cdn.com/v4/letter/s/c37758/32.png) [@Simplicio](https://boards.straightdope.com/u/Simplicio)\
**Post date:** [July 12, 2012, 2:04am UTC](https://boards.straightdope.com/t/i-need-help-in-calculus-need-consensus-fast/627950/5 "2012-07-12T02:04:10Z")

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> [@Sue\_Duhnym](#):
>
> There’s a “no homework” rule? Well, shit. Sorry mods. Feel free to close this if I’ve violated it. I apologize.

I’m pretty sure just asking for help (as opposed to trying to just get answers) isn’t against the rule.

And I think there’s one typo in your posted answer but otherwise I get the same thing.

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**Author:** ![Sue\_Duhnym](https://avatars.discourse-cdn.com/v4/letter/s/91b2a8/32.png) [@Sue\_Duhnym](https://boards.straightdope.com/u/Sue_Duhnym)\
**Post date:** [July 12, 2012, 2:06am UTC](https://boards.straightdope.com/t/i-need-help-in-calculus-need-consensus-fast/627950/6 "2012-07-12T02:06:12Z")

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> [@Topologist](#):
>
> There’s one mistake I see. I’ll just point out that you should be using the product rule on x[sup]3[/sup]h[sup]2/sup and you’ve made a mistake in doing so.

Oooohhhh.

{fʹg(x) \* gʹ(x)}+ {3x[sup]2[/sup]h[sup]2/sup + x[sup]3[/sup]2h(x) \* hʹ(x)}

Thanks for the assist on formatting, too. That was one of the other problems I missed, I was using implicit differentiation and totally forgot something like 3xy means the product rule. I made a lot of stupid, elementary mistakes (bangs head on desk).