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HallsofIvy
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Today,
04:42
MarkFL
replied to a thread
BBCode For Username HTML Markup
in
vBulletin Products
Update - Version 1.3: SEO friendly links to user profiles. vBulletin's intrinsic username markup function used. Username matching is now...
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1 replies | 45 view(s)
Yesterday,
22:53
MarkFL
replied to a thread
Prove a number is divisible by a number?
in
Number Theory
Another approach would be to use the binomial theorem: 7^n-1=(6+1)^n-1=6\sum_{k=1}^{n}\left({n \choose k}6^{k-1}\right)
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7 replies | 81 view(s)
Yesterday,
14:51
MarkFL
replied to a thread
AlphaZero Crushes Chess
in
Chat Room
That's amazing! (Yes)
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2 replies | 38 view(s)
Yesterday,
14:38
MarkFL
replied to a thread
limit of a series
in
Calculus
As suggested, I would continue on your current path, but I wanted to show how I would approach the problem... I would begin by expressing the...
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3 replies | 44 view(s)
Yesterday,
11:59
MarkFL
replied to a thread
Need help with reversal of a calculation involving gravitational constant.
in
Pre-Algebra and Algebra
It's actually: G=\frac{rV_e^2}{2M}
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6 replies | 67 view(s)
Yesterday,
01:55
MarkFL
replied to a thread
Revenue and Cost and Profit Problem
in
Business Mathematics
To follow up: The axis of symmetry is: x=-\frac{48}{2(-2)}=12 We see that the profit function opens downward, and so the vertex is the...
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3 replies | 44 view(s)
December 10th, 2017,
12:30
MarkFL
replied to a thread
Revenue and Cost and Profit Problem
in
Business Mathematics
Another approach would be to express your profit function in vertex form: P(x)=-a(x-h)^2+k where: P_{\max}=k
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3 replies | 44 view(s)
December 10th, 2017,
00:57
MarkFL
replied to a thread
Revenue and Cost and Profit Problem
in
Business Mathematics
Your profit function is correct: P(x)=-2x^2+48x-108 Now, what I would do is find the axis of symmetry (since the vertex lies on this...
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3 replies | 44 view(s)
December 9th, 2017,
17:06
MarkFL
replied to a thread
m2215b.14 Find the limiting velocity
in
Calculus
If the hyperbolic tangent factor goes to 1, then the terminal velocity $v_T$ must be: v_T=\sqrt{\frac{mg}{k}} Dimensional analysis shows that...
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13 replies | 165 view(s)
December 9th, 2017,
15:05
MarkFL
replied to a thread
m2215b.14 Find the limiting velocity
in
Calculus
Yes, and so what does this tell you about the terminal velocity?
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13 replies | 165 view(s)
December 9th, 2017,
09:00
HallsofIvy
replied to a thread
Intersection of all subspace of V is the empty set
in
Linear and Abstract Algebra
But that isn't what we want. That is "the set whose only member is the empty set". The "intersection of all subspaces of V" is the set whose only...
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8 replies | 239 view(s)
December 9th, 2017,
08:12
MarkFL
replied to a thread
Need help with reversal of a calculation involving gravitational constant.
in
Pre-Algebra and Algebra
Hello, and welcome to MHB, Edwin! (Wave) We are given: V_e=\sqrt{\frac{2GM}{r}} What do we get if we square both sides of the equation?
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6 replies | 67 view(s)
December 8th, 2017,
20:08
MarkFL
replied to a thread
m2215b.14 Find the limiting velocity
in
Calculus
Yes, so what's the limit: \lim_{u\to\infty}\tanh(u)\,?
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13 replies | 165 view(s)
December 8th, 2017,
02:39
MarkFL
replied to a thread [SOLVED]
M2215b.08 Find the volume of the solid (shell meithod)
in
Calculus
Let's check your result using the washer method: V=\pi\left(\int_0^{\sin\left(\frac{\pi^2}{4}\right)}...
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8 replies | 97 view(s)
December 7th, 2017,
22:14
MarkFL
replied to a thread [SOLVED]
M2215b.08 Find the volume of the solid (shell meithod)
in
Calculus
You originally had the integrand correct, but when you corrected the limits, you changed the integrand such that the integral was still incorrect...
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8 replies | 97 view(s)
December 7th, 2017,
17:54
MarkFL
replied to a thread [SOLVED]
M2215b.08 Find the volume of the solid (shell meithod)
in
Calculus
Now, reverse the change you made to the integrand...
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8 replies | 97 view(s)
December 7th, 2017,
17:49
MarkFL
replied to a thread [SOLVED]
M2215b.08 Find the volume of the solid (shell meithod)
in
Calculus
Examine your limits of integration more closely...:)
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8 replies | 97 view(s)
December 7th, 2017,
14:28
MarkFL
replied to a thread
m2215b.14 Find the limiting velocity
in
Calculus
No, I was thinking more along the lines of: \tanh(u)\equiv\frac{e^{u}-e^{-u}}{e^{u}+e^{-u}} What happens if you multiply that by: ...
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13 replies | 165 view(s)
December 7th, 2017,
13:44
MarkFL
replied to a thread
m2215b.14 Find the limiting velocity
in
Calculus
Okay, now the given velocity function is dimensionally consistent, given that $k$ has units of mass per length (can you demonstrate this?). In...
see more
13 replies | 165 view(s)
December 7th, 2017,
13:29
MarkFL
replied to a thread
Require Edit Reason
in
vBulletin Products
Update - Version 1.3: Add ability to exempt all usergroups from being required to edit, to allow for the setting of pre-defined edit reasons...
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1 replies | 65 view(s)
December 6th, 2017,
21:13
MarkFL
replied to a thread
m2215b.14 Find the limiting velocity
in
Calculus
You've given a constant velocity here...
see more
13 replies | 165 view(s)
December 6th, 2017,
11:36
HallsofIvy
replied to a thread [SOLVED]
30 Calculate the book value per share
in
Business Mathematics
The original mistake was not "arithmetic" but perhaps not understanding what "liabilities" are. Liabilities are money you owe so you subtract...
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8 replies | 180 view(s)
December 6th, 2017,
11:30
HallsofIvy
replied to a thread
grade 12 financial math
in
Business Mathematics
Three years has only 12 quarters so it is not that hard to do it "by hand". For the first quarter, 50000 was invested at .0775/4= 0.019375. ...
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2 replies | 63 view(s)
December 6th, 2017,
11:07
HallsofIvy
replied to a thread
243.12.7.12 plane from 3 points
in
Calculus
In your first post you wrote "\left|\begin{array}{ccc} \vec{i} & \vec{j} & \vec{k} \\ 8 & -15 & -19 \\ 2 & -13 & 23\end{array}\right|= " without...
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5 replies | 80 view(s)
December 6th, 2017,
10:51
HallsofIvy
replied to a thread
Algebraic expression simplification
in
Pre-Algebra and Algebra
Notice that this equivalence is true only if v+ 2u\ne 0.
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4 replies | 100 view(s)
December 6th, 2017,
10:43
HallsofIvy
replied to a thread
Which is the parametrization σ?
in
Calculus
well, I expect that the key point here is that the vector (1, 1, 1) is perpendicular to the plane x+ y+ z= 1. And notice that, of course, the...
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3 replies | 50 view(s)
December 6th, 2017,
09:42
HallsofIvy
replied to a thread
Which is the parametrization σ?
in
Calculus
Doesn't that depend on exactly what the function, g, is?
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3 replies | 50 view(s)
December 5th, 2017,
13:41
HallsofIvy
replied to a thread
Intersection of all subspace of V is the empty set
in
Linear and Abstract Algebra
By the way, the title to this thread said "empty set". Obviously, {0} is not the "empty set".
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8 replies | 239 view(s)
December 5th, 2017,
06:22
MarkFL
replied to a thread
Area between the curve and x axis
in
Calculus
Yes that's correct: W|A - area between x-axis and y=2/(x-1)-1 on Note: W|A returns a result in a different form, but is recognizable as...
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8 replies | 128 view(s)
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December 9th, 2017
08:53 -
HallsofIvy
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Re: Calculate integral using Stokes Theorem
by
I like Serena
We have that $x^2+y^2=1...
December 8th, 2017
07:59 -
HallsofIvy
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Re: m2215.12 length of curve
by
skeeter
$\begin{align*}\displayst...
December 6th, 2017
17:21 -
karush
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Re: 243.12.7.12 plane from 3 points
by
HallsofIvy
In your first post you...
16:57 -
Joppy
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Re: Algebraic expression simplification
by
HallsofIvy
Notice that this...
15:09 -
greg1313
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Re: Algebraic expression simplification
by
HallsofIvy
Notice that this...
12:09 -
MarkFL
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Re: Algebraic expression simplification
by
HallsofIvy
Notice that this...
12:08 -
Nightspider
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Re: Algebraic expression simplification
by
HallsofIvy
Notice that this...
10:49 -
HallsofIvy
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Re: Algebraic expression simplification
by
Joppy
Hi All I am trying to...
December 3rd, 2017
12:32 -
karush
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Re: 243.14.7.4 Find all local extreme values
by
HallsofIvy
$f(x,y)= x^2+ 14x+ y^2-...
08:03 -
HallsofIvy
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Re: Standard Deviation Sets
by
tkhunny
1.914 And THIS is why...
December 2nd, 2017
22:00 -
tkhunny
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Re: Standard Deviation Sets
by
HallsofIvy
If an approximation is...
December 1st, 2017
12:38 -
HallsofIvy
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Re: Standard Deviation Sets
by
tkhunny
Super Rough (but...
November 29th, 2017
16:39 -
greg1313
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Re: x4.6 Find the extrema of f(x, y, z) = x + yz
by
HallsofIvy
OR you can use the...
07:26 -
greg1313
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Re: Union and set rules
by
HallsofIvy
In brief, all of those...
November 28th, 2017
14:49 -
karush
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Re: 243.13.01.18 motion of a particle
by
HallsofIvy
More simply, if two...
14:07 -
TinaSprout
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Re: Union and set rules
by
HallsofIvy
In brief, all of those...
November 25th, 2017
15:42 -
HallsofIvy
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Re: dy/dx ln2xy=e^{x+y}
by
MarkFL
Find $\frac{dy}{dx}$ ...
13:29 -
greg1313
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Re: Question from Past Paper
by
HallsofIvy
Then where in the world...
November 24th, 2017
07:30 -
Peter
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Re: Nonreflexive Relation ...
by
HallsofIvy
In the example given,...
November 21st, 2017
20:12 -
HallsofIvy
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Re: Sequence challenge
by
castor28
Let the sequence...
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