Facebook Page
Twitter
RSS
Tab Content
  • topsquark's Avatar
    Today, 17:39
    You can do it by hand: A = \frac{-b + \sqrt{b^2 - 4ac}}{2a} B = \frac{-b - \sqrt{b^2 - 4ac}}{2a} Add them together and you get A + B = -b/a. ...
    1 replies | 13 view(s)
  • MarkFL's Avatar
    Yesterday, 12:24
    Just to follow up, here is the completed table: Sum $S$ Probability of $S$: $P(S)$ Net Gain/Loss (in dollars) $G$ Product $G\cdot P(S)$
    2 replies | 79 view(s)
  • MarkFL's Avatar
    March 26th, 2017, 22:32
    MarkFL replied to a thread Radius of Circle in Pre-Calculus
    That is the radius of the circle after it has been increased by $a$ units. If I tell you that my weight increased by 20 lbs., then you know my...
    4 replies | 84 view(s)
  • Jameson's Avatar
    March 26th, 2017, 22:19
    Hi tmt, (Wave) For the quoted part in bold, should this read "If all cars are reserved for the day..."? I think there are two events here,...
    1 replies | 49 view(s)
  • MarkFL's Avatar
    March 26th, 2017, 21:35
    MarkFL replied to a thread Radius of Circle in Pre-Calculus
    Let's let $0<a$ be the number units the radius must be increased. And so the change in area we can write as: \Delta A=\pi(r+a)^2-\pi r^2=b Now...
    4 replies | 84 view(s)
  • topsquark's Avatar
    March 26th, 2017, 20:41
    Looks good. -Dan
    2 replies | 40 view(s)
  • MarkFL's Avatar
    March 25th, 2017, 21:53
    MarkFL replied to a thread The Distance Across in Geometry
    \overline{MK}=\sqrt{(\sqrt{2}a)^2+(\sqrt{2}b)^2}=\sqrt{2\left(a^2+b^2\right)}=\sqrt{2(50)}=\sqrt{100}=10 :D
    8 replies | 91 view(s)
  • topsquark's Avatar
    March 25th, 2017, 21:31
    At a guess you are forgetting about the cross term. (a + b)^2 \neq a^2 + b^2. It is (a + b)^2 = a^2 + 2ab + b^2. You are going to end up having to...
    4 replies | 60 view(s)
  • MarkFL's Avatar
    March 25th, 2017, 21:07
    MarkFL replied to a thread Lagrange Multipliers 2 in Calculus
    I arbitrarily chose another point on the constraint, so that we could do a comparison like I mentioned just now in the other thread. :D
    9 replies | 90 view(s)
  • MarkFL's Avatar
    March 25th, 2017, 21:04
    MarkFL replied to a thread Lagrange Multipliers in Calculus
    I chose the point as it is on the constraint. Using that point, we can determine if our one critical point is a maximum or a minimum. If the...
    9 replies | 75 view(s)
  • MarkFL's Avatar
    March 25th, 2017, 19:21
    MarkFL replied to a thread Lagrange Multipliers 2 in Calculus
    I agree that the point $(2,2)$, is the only one that meets all criteria. Now we need to compare the value of $f$ at another point on the constraint,...
    9 replies | 90 view(s)
  • MarkFL's Avatar
    March 25th, 2017, 19:08
    MarkFL replied to a thread Lagrange Multipliers in Calculus
    I agree that of the 3 critical points, $(1,1)$ is the only one in quadrant I. Now, we know this is either a maximum or a minimum, and to determine...
    9 replies | 75 view(s)
  • MarkFL's Avatar
    March 25th, 2017, 11:15
    MarkFL replied to a thread Factoring...6 in Pre-Calculus
    It might be more clear to state something like the following: The difference of cubes formula states: p^3-q^3=(p-q)\left(p^2+pq+q^2\right) ...
    5 replies | 77 view(s)
  • MarkFL's Avatar
    March 25th, 2017, 10:47
    MarkFL replied to a thread Lagrange Multipliers 2 in Calculus
    Consider: e^u=0 What do you get when solving for $u$? Okay, you correctly found $x^2=y^2$...what do you get when you substitute for...
    9 replies | 90 view(s)
  • MarkFL's Avatar
    March 25th, 2017, 10:39
    MarkFL replied to a thread Lagrange Multipliers in Calculus
    What I would do is use the constraint to determine $y=2-x$. Now substitute for $y$ in both equations you mentioned, and solve for $x$, then your...
    9 replies | 75 view(s)
  • MarkFL's Avatar
    March 25th, 2017, 02:30
    This is a calculus question...please don't continue to post calculus questions in other forums. If given: ...
    3 replies | 87 view(s)
  • topsquark's Avatar
    March 24th, 2017, 23:16
    topsquark replied to a thread Factoring...7 in Pre-Calculus
    I mentioned this in another thread. Don't set the LHS of "a = a + b" It's too confusing. -Dan
    3 replies | 49 view(s)
  • topsquark's Avatar
    March 24th, 2017, 23:13
    topsquark replied to a thread Factoring...6 in Pre-Calculus
    You need to clarify your variables. "b = (a - b)" isn't right. Pick a variable name, say, p... Anything but that b on the LHS.... Then you have p...
    5 replies | 77 view(s)
  • MarkFL's Avatar
    March 24th, 2017, 23:12
    MarkFL replied to a thread Lagrange Multipliers 2 in Calculus
    If you solve both equations for $\lambda$ and then equate the results, you obtain: \frac{ye^{xy}}{2x}=\frac{xe^{xy}}{2y} Multiply through by 2:...
    9 replies | 90 view(s)
  • MarkFL's Avatar
    March 24th, 2017, 21:24
    MarkFL replied to a thread Lagrange Multipliers in Calculus
    Okay, so what this implies is: \frac{x}{\sqrt{6-x^2-y^2}}=\frac{y}{\sqrt{6-x^2-y^2}} Cross-multiply: x\sqrt{6-x^2-y^2}=y\sqrt{6-x^2-y^2} ...
    9 replies | 75 view(s)
  • topsquark's Avatar
    March 24th, 2017, 21:05
    topsquark replied to a thread Factoring...5 in Pre-Calculus
    Yeppers! -Dan
    2 replies | 35 view(s)
  • MarkFL's Avatar
    March 24th, 2017, 16:18
    MarkFL replied to a thread The Distance Across in Geometry
    Using the Pythagorean theorem, we find: \overline{MK}=\sqrt{(\sqrt{2}a)^2+(\sqrt{2}b)^2}=\sqrt{2\left(a^2+b^2\right)} Now, we know that...
    8 replies | 91 view(s)
  • MarkFL's Avatar
    March 24th, 2017, 06:10
    MarkFL replied to a thread [SOLVED] Minimum of function under constraint in Calculus
    I would use W|A: W|A - optimize 2x+y subject to xy=18
    8 replies | 262 view(s)
  • MarkFL's Avatar
    March 24th, 2017, 04:29
    The objective function is linear, so it describes a plane, and so I don't believe there will be any saddle points, or in fact any critical points...
    4 replies | 63 view(s)
  • MarkFL's Avatar
    March 24th, 2017, 04:04
    MarkFL replied to a thread Boat direction in Calculus
    Is this a calculus-based physics course?
    6 replies | 100 view(s)
  • MarkFL's Avatar
    March 24th, 2017, 01:37
    What I would do is observe that we have cyclical symmetry, that is we may interchange $x_1$ and $x_2$ with no change in either the objective function...
    4 replies | 63 view(s)
  • MarkFL's Avatar
    March 24th, 2017, 01:25
    MarkFL replied to a thread The Distance Across in Geometry
    Not quite...it would be \sqrt{2}a and \sqrt{2}b...so what would the diagonal of the rectangle be?
    8 replies | 91 view(s)
  • MarkFL's Avatar
    March 23rd, 2017, 21:17
    MarkFL replied to a thread The Distance Across in Geometry
    I would let $a$ be the length (in cm) of the segments with 1 tick mark, and $b$ be the length (in cm) of the segments with 2 tick marks. And so,...
    8 replies | 91 view(s)
  • MarkFL's Avatar
    March 23rd, 2017, 19:30
    MarkFL replied to a thread Boat direction in Calculus
    Being that it is an optimization problem, on a function in two variables, the way I worked it using the calculus is the most straightforward way I...
    6 replies | 100 view(s)
More Activity

2 Visitor Messages

  1. Reply/View Conversation
    Hello and welcome back to MHB, soroban!

    We are happy to see that you have returned, and we look forward to your continued participation here!

    On Behalf Of MHB's Staff,

    Jameson.
  2. Reply/View Conversation
    No such thing as an ex-Marine...
Showing Visitor Messages 1 to 2 of 2
About soroban

Basic Information

About soroban
Biography:
Retired math professor, ex-Marine, Nisei
Location:
Lexington, MA, USA
Interests:
Science fiction, hunor, music
Occupation:
retired

Statistics


Total Posts
Total Posts
409
Posts Per Day
0.22
Thanks Data
Thanks Given
167
Thanks Received
1,388
Thanks Received Per Post
3.394
Visitor Messages
Total Messages
2
Most Recent Message
May 14th, 2016 23:24
General Information
Last Activity
January 5th, 2017 23:57
Last Visit
November 24th, 2016 at 00:42
Last Post
November 9th, 2016 at 11:39
Join Date
February 2nd, 2012

11 Friends

  1. abender Offline

    MHB Apprentice

    abender
  2. alane1994 Offline

    MHB Craftsman

    alane1994
  3. earboth Offline

    MHB Apprentice

    earboth
  4. Fantini Offline

    MHB Craftsman

    Fantini
  5. Jameson Offline

    Администратор

    Jameson
  6. MarkFL  Online

    Pessimist Singularitarian

    MarkFL
  7. masters Offline

    MHB Apprentice

    masters
  8. sbhatnagar Offline

    MHB Apprentice

    sbhatnagar
  9. Sudharaka Offline

    MHB Master

    Sudharaka
  10. topsquark  Online

    MHB Journeyman

    topsquark
Showing Friends 1 to 10 of 11
Page 1 of 2 12 LastLast

March 28th, 2017


Ranks Showcase - 3 Ranks
Icon Image Description



Name: MHB Chat Room Award (2014)
Issue time: January 3rd, 2015 15:30
Issue reason:



Name: MHB Chat Room Award (Jul-Dec 2013)
Issue time: January 5th, 2014 16:54
Issue reason:



Name: MHB Humor Award (Jan-June 2013)
Issue time: July 1st, 2013 22:16
Issue reason:
Math Help Boards