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FragKrag
United States11566 Posts
New Problem:X^3+Y^3=125 dy/dx =? a. -x/y b.-x/5y c. y/x d. x/(y-5) e. x/y Well, I thought it was -(x/y)^2, but it's not on there. I think that it should be negative, and there should not be a 5, which leaves me -x/y, which is x^2+y^2=C a. [8,10) b. (2,10) c. [2,10] d. [2,10) e. (2,10] halps would be appreciated <3 Edit: What we got is that since [8,10) has a continuous slope of 1, it's right.   | ||
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Saracen
United States5139 Posts
if the sharp point from the absolute value is included in your set of points, then no if not, then yes | ||
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doghunter
United States23 Posts
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Avidkeystamper
United States8556 Posts
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FragKrag
United States11566 Posts
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doghunter
United States23 Posts
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vAltyR
United States581 Posts
man, that's a *precalc* question? we never covered that until calculus. in fact, i never even heard the word "derivative" until i opened a calc book. | ||
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thunk
United States6233 Posts
On October 01 2008 13:32 doghunter wrote: There's no limit from the left side, so you can't say that there is a limit at x=8 It's continuous and the limit as x approaches 8 exists. It's just no differentiable because the derivative from the right and the derivative from the left are inequal. | ||
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Purind
Canada3562 Posts
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SIUnit
China288 Posts
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FragKrag
United States11566 Posts
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skyglow1
New Zealand3962 Posts
x^3+y^3=125 Differentiation both sides by x: 3x^2+d(y^3)/dx=0 Since y is a function of x, and using chain rule: d(y^3)/dx = 3y^2 x dy/dx So you get: 3x^2 + 3y^2 x dy/dx = 0 And rearranging: dy/dx = -3x^2/3y^2 [Edit] I'm a retard -_- | ||
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SaveYourSavior
United States1071 Posts
but a seems to be the right answer since it seems the most right | ||
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Divinek
Canada4045 Posts
On October 22 2008 13:46 skyglow1 wrote: Use implicit differentiation which involves chain rule. x^3+y^3=125 Differentiation both sides by x: 3x^2+d(y^3)/dx=0 Since y is a function of x, and using chain rule: d(y^3)/dx = 3y^2 x dy/dx So you get: 3x^2 + 3y^2 x dy/dx = 0 And rearranging: dy/dx = -3x^2/3y^2 = -x/y so the answer should be a) Implicit differentiation is in pre calc? | ||
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Ecael
United States6703 Posts
If memory serves schools in Taiwan covered power rule to implicit differentiation in precalc, at least that's what I recall of what my friends/parents/family's talks of how they had it tough :p EDIT - It'd be hilarious when OP posts to say how he isn't at Taiwan though.  | ||
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FragKrag
United States11566 Posts
I'm taking "PreCalculus". It's the course name, but the book has PreCalc and Calc I so lol tt;; anyways, how can you go from -(x/y)^2 to -x/y? ?:/ | ||
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skyglow1
New Zealand3962 Posts
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FragKrag
United States11566 Posts
Today my math teacher tells me that "abcde" is a choice when you cant find the answer. --; | ||
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onihunter
United States515 Posts
On October 23 2008 09:49 FragKrag wrote: ;_________; Today my math teacher tells me that "abcde" is a choice when you cant find the answer. --; Nice, would explain a lot about why I couldn't figure this problem out lol. And man I hate it when math questions have "None of the above" as a choice. | ||
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Ecael
United States6703 Posts
On October 23 2008 09:49 FragKrag wrote: ;_________; Today my math teacher tells me that "abcde" is a choice when you cant find the answer. --; Ah good, I was going a bit insane and trying to log this through to solve earlier. | ||
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