Recent content by Steve10

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    Solve 2^x=x^2+7 | Find x Without Differentiation

    2^x = x^2 + 7 2^x - x^2 - 7 = 0 Now use the http://www.shodor.org/UNChem/math/Newton/index.html" to find root(s) of f(x) = 0 If the eqn, 2^x=x^2+7, looks simple enough you could try simple substitution. x=1: 2 = 1 + 7 -- nope, lhs too small x=2: 4 = 4 + 7 -- nope, lhs too small x=3...
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    Solving the Inequality Problem: Finding the Solution Set for x/(2-x)<4 | Skook"

    Start by multiplying both sides by (2-x). However you must bear in mind that, depending upon the possible values of x, that the term (2-x) could be either positive or negative. And, when you divide an inequality by a negative number, then you change the direction of the inequality symbol.
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    Solve 6th Grade Enigma with Integers 8, 4, 2, 1 in Order

    Since I can't do this problem, then thanks for saying it seems inpossible as it is. Factorial function not included, I'm afraid :(, nice one though :) AFAIK == As Far As I Know. AFAIAA == As Far As I Am Aware.
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    Solve 6th Grade Enigma with Integers 8, 4, 2, 1 in Order

    I would guess that the order of operands is simply that the use of the operands should follow that order of preference. + - % X ^. Nice answers. It's just that the integers are only allowed to be used once only - AFAIK!
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    Solve 6th Grade Enigma with Integers 8, 4, 2, 1 in Order

    This is supposed to be a 6th grade problem. using integers 8 4 2 1 in order, create an equation to equal 18 and another to equal 19. you may use + - % X and exponents (^) in the same order. Now if the integers and operands (including exponent) are to be in any order then the answers are...
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    Calculating Expectation for a Random Walk with a Time-Varying Function

    Thanks, I should have mentined that about mu. It is a constant value. So I was correct after all. :smile: I guess that's just as well, since I'm already typing up my results based on that conclusion! Many thanks for the confirmation.
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    Calculating Expectation for a Random Walk with a Time-Varying Function

    I have a random function f(n) which takes the values +/- 1 with equal probability. Let the variable X take the sum of the values of f(n) after n steps. Then I can write, X(T) = \sum_{n=0}^T f(n) where T = 0,1,2,... and X(0) = 0. And I can write the expectation of X as, <X> = < \sum_{n=0}^T...
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    Solving Statistics with PDFs: Retiring 11 Cars/Week After 6 Years

    Ive never heard of marginal and joint pdf's :frown: I did my convolution though and got the right answer :smile: Many thanks for the help.
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    Solving Statistics with PDFs: Retiring 11 Cars/Week After 6 Years

    Thanks. Working backwards from that statement makes sense of the previous parts, viz psup(t) = 1/5, 0<=t<=5, zero otherwise. The mark scheme for this question is, (a) [5] (b) [4] (c) [10] (d) [6] For part (c) I'm to use a convolution. I should do, pret = pser⊕psup Where I'm...
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    Solving Statistics with PDFs: Retiring 11 Cars/Week After 6 Years

    Is this correct ? When doing part (b), I got (with some help from elsewhere) that the probability of any given car being suppplied (t<5) is P = t/1000. I believe that the probability is defined as, P(t1,t2) = int[t1 to t2] psup(t) dt where P(t1,t2) is the probability that a car will be...
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    Solving Statistics with PDFs: Retiring 11 Cars/Week After 6 Years

    Thanks. That gives me the right answer. p(6) works out at 0.11624 which gives 11.18 pro woche. I've got the answer now, but I still don't understand this stats stuff. I'm pretty good at other maths disciplines, but I just can't seem to follow the "logic" of statistical reasoning. Anyway...
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    Solving Statistics with PDFs: Retiring 11 Cars/Week After 6 Years

    Here's the full question. A car rental company signs a contract to take delivery of a new model starting in January 2006, at the rate of n = 1000 cars per year, until the contract ends, after T = 5 years, in January 2011. The cars are removed from service when they are damaged or start to...
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    Solving Statistics with PDFs: Retiring 11 Cars/Week After 6 Years

    Sorry, the pdf I gave is for retiring a car, t years after the start of the program (t=0), where the program is the supply of cars at 1000 cars/year for 5 years. This supply is to be taken as a constant rate. The pdf that a given car will be retired after t' years of service/use is...
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    Solving Statistics with PDFs: Retiring 11 Cars/Week After 6 Years

    A car rental company receives cars at n = 1000 cars/year for the first 5 years and none thereafter. The pdf for retiring a car is, p(t) = (1/5)(1 - exp(-t/3)) , 0<t<5 = (1/5)(exp[-(t-5)/3] - exp(-t/3)) , t > 5 Show that after 6 years cars are being retired from the...
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