Exponential Definition and 1000 Threads

I have been stuck at this calculation. There are two exponential distributions X and Y with mean 6 and 3 respectively. We need to find E[y-x|y>x] I keep getting it negative, which is clearly wrong. Anybody wants to try it?

My friend just came to me with this problem: e^x + e^-x = 4 I aced precalc, and I still have no idea where to start on this one. I've factored, natural logged, factored and then natural logged... and I keep running into dead ends. My graphing calculator puts the answer at +/-1.3169 or...

Homework Statement P(r) = 1-(2r2+2r+1)e-2r i know that p(r) is just the derivative of P(r) to find the median i would just integrate from o to r and set that equal to .5 but when you integrate youre just going back to P(r) from 0 to r so i get 1-(2r2+2r+1)e-2r = .5 how would...

Homework Statement lim_{x->0} (1+ sin5x)^{cotx} Homework Equations that's the problem.. I don't know :s The Attempt at a Solution can't think of any theorems or any methods I could use here.. what should I do? thank you

Homework Statement Trying to solve for K: ln(1-4k)=-6k Homework Equations The Attempt at a Solution I know that need to take the e of both side, to get 1-4k=e^-6k, but I cannot remember any properties of e to allow me to remove the k from the exponent. Any tips is appreciated.

So I was playing around with logarithmic & exponential amplifiers in my lab class. I was looking at the following equations: http://upload.wikimedia.org/math/7/7/6/77663157d5b97ceb2e3edac5f587a620.png and http://upload.wikimedia.org/math/b/3/c/b3c569c85552561e41dec916f6e8ebe8.png...

Homework Statement Hello i am doing a cooling experiment and i want to know the following: y=28.49e^(-0.03890*800) +26.51 (note the 26.51) is not part of the exponential. What is y? and I was wondering whether this would go ever go through the x axis? Thanks people! Homework...

Homework Statement Find the second derivative of: e^{ax} and e^{-ax} Homework Equations The Attempt at a Solution The book that I am using seems to have been very vague on how to take the derivatives of exponential functions. I am aware that: \frac {d(e^{x})}...

How would you integrate something like xe(x^2) by using a substitution like u=x^2

Exponential Equation! -Stuck!- 1. 32y+3 = 3y+5 The Attempt at a Solution 2y + 3 = y+5 2y = y+2 I really don't think I am doing this right, I am trying to find the value of Y. the answer is 2 but I don't know how to come up with the answer.

Hi, I have the equation y'' +4y = t~sin(t) i know that you usually guess the solution by substituting y for a polynomial (or whatever the form of the right side is). But i want to do this by using the exponential function exp. so, set y to equal te^{it} chain rule:y^{\prime} = 1...

Homework Statement We have the ODE y' = -ky + R for a population y(t) where death rate exceeds birth rate, counteracted by a constant restocking rate. I'm assuming k is the decay constant and R is the restocking rate The population at time t0 = 0 is y0, and I have to find a formula for...

Homework Statement how would you integrate, int (-ik - 2ax)*exp(-2ax^2) dx with limits infinity - infinity Homework Equations i think i can use the result int exp(-x^2) dx = sqrt (pi). But I am stumped. The Attempt at a Solution i thought about multiplying it out int...

Hello! I found on this webpage: http://www-thphys.physics.ox.ac.uk/people/JohnCardy/qft/costate.pdf page 1, on the bottom that e^{\phi^* a } f(a^{\dagger} , a ) = f(a^{\dagger} + \phi^*, a) e^{\phi^* a } I have tried to prove this, writing both as taylor series, but the problem is to...

Homework Statement Let z=x+iy prove that Exp[z1]*Exp[z2]=Exp[z1+z2] Homework Equations Binomial thm (x+y)^n=Sum[Bin[n,k]*x^n-k*y^k,{k,1,n}] The Attempt at a Solution I have no idea about this question... Please give me some help.

I'm just a neuroscientist, so forgive me if the answer to this question is either obvious, or the answer is that it is impossible, obviously. Basically, this image should outline the question clearly http://img713.imageshack.us/img713/2569/mathsissuefixedyxs.gif (And Y0 is always 1)Also, I...

I am reading conflicting interpretation of the Hubble constant in the exponentially expanding accelerating universe. Some say the Hubble constant is continuing to decrease; while others say Hubble constant is now unchanging and has become truly a constant. Which is correct?

can someone please explain the difference. Graphically and mathematically it is easy to see they are inverses. But I see certain scales like the Richter scale that seem to increase exponentially, but are labeled as logarithmic scales. for example, on the richter scale with each increase in...

Homework Statement I am working on a problem, and there is a small step I need help on: I have the expression eab, where a is a constant, and b is a variable. I need to separate a and b so I can pull out the expression b from an integral expression. Is there any exponent law or manipulation...

Can someone give me a starter hint for this problem? Brain's not working at full speed... 3^(2x) - 2*3^(x+5) + 3^10 = 0 Thanks

Homework Statement Homework Equations The Attempt at a Solution Ive numbered the solution steps, the ones that are giving me trouble are from 1 to 2 and from 3 to 4 From 1 to 2 i don't understand how there can be an exp(x) term taken out of the bracket and still be in the...

hi guys I need The proof from definition of the derivative for exponential and log Fn can somebody help me !

Homework Statement Briefly, the question asks to prove how the interference of 2 electrons (travelling in opposite directions as 1-D waves) would affect the probability of finding each electron in free space. My issue has to do with the first step in the solution. Homework Equations...

Homework Statement problem 1 diff([f(tanx)], x) = x^2; prove that diff[f(u)]=(tan^-1(u))^2/(1+u^2) problem 2 int(f(u), u = 0 .. 1) = f(t)-1; prove that f(a+b)=f(a)f(b) for every a,b ∈R The Attempt at a Solution problem 1 i don't know how to answer this...

I am learning calculus from a book of mine, and it gave an example problem of exponential growth (as derived from the exponential differential equation of dy/dx = ky to be y=Ce^kt) saying a population is growing at a rate of 2% per year, and says that K, the growth constant, in this case is k =...

Homework Statement I don't understand why they took M(e)=1 , and how the proceed on with the proof. Thanks in advance(= Homework Equations The Attempt at a Solution

f(x) = 2^x \left \left f(kx) = 2^(kx) \left \left b = 2^k \left \left b^x = 2^(kx) \left \left b^x = f(kx) \frac{d}{dx}(b^x) = \frac{d}{dx}(f(kx)) = \frac{d}{dx}(2^(kx)) (1) \frac{d}{dx}(f(kx)) = k.f'(kx) (2) I can't see how step (1) gets to step (2). Because I thought...

Homework Statement Hi all Is infinity a minimum of the exponential function f(x)=ex or not? I personally do not think so since it is a limit, but I wanted to ask you guys to be 100% sure.

Are there any general methods to solve the following complex exponential polynomial without relying on numerical methods? I want to find all possible solutions, not just a single solution. e^(j*m*\theta1) + e^(j*m*\theta2)+e^(j*m*\theta3) + e^(j*m*\theta4) + e^(j*m*\theta5) = 0 where...

Homework Statement \frac { d^2 \theta }{d x'^2 } = -y *exp(\theta) eq. 1 mayb be integrated to yield exp(\theta) = \frac {a}{cosh^2(b \frac{+}{-} \sqrt \frac{a*y}{2} * x')} \theta = f(y,x') Homework Equations The Attempt at a Solution the exponent is throwing me off, but i probably...

Let X1, X2, ...Xn be independent exponential variables having a common parameter gamma. Determine the distribution of min(X1,X2, ...Xn). The Attempt at a Solution I know how to do it with one X and one parameter but I am at a loss with these multiple ones... Thanks so much!

Homework Statement -Find the intervals on which f is increasing or decreasing -Find the local maximum and minimum values of f -Find the intervals of concavity and the inflection points f(x)=xex f'(x)= ex+xex then I must solve for x when the function equals zero to find my critical numbers...

I have been given a Indice. I've been trying to figure it out for awhile and need some assistance, It'd be great if someone could work it out and show me the steps they did and even explain it. ([a-2b-3/ 2a3b-4]2 )/ [ab-15]/a-3b2]) I've attempted the working out in my book, Its abit hard...

Hello all, I am trying to solve an integral with Mathematica, but I do not succeed. I am wondering whether the integral cannot be solved, or whether Mathematica cannot solve the integral, or whether I am doing something wrong. Details: * Mathematica does not seem to be able to solve the...

Homework Statement y=9-x Homework Equations The Attempt at a Solution dy/dx=-9-xln9 We are provided with the answers. I do not understand the concept behind how to get from the question to the solution. What rule(s) are applied? If somebody could solve this single question...

Homework Statement i have to integrate e^(-y) / y and i found out that you have to use this exponential integral and someone else said it doesn't have an integral. either way I am thoroughly confused The Attempt at a Solution i have no clue what so ever. The original question had it in...

Homework Statement lim e3/(2-x) x->2+ The Attempt at a Solution I can't seem to get started on this one.

Homework Statement The bus service operates between points A and B. The buses depart from the terminal station A with headways that follow the negative exponentioal distributiona with parameter 10 trips per hour. Assume that the characteristics of the system remain the same over time (not...

Hi all, I'm trying to solve the definite integral between 0 and inf of: exp(a*x^2 + b*x + c) --------------------- dx 1 + exp(m*x + n) with a,b,c,m,n real numbers and a < 0 (negative number so it converges). I've read in the forum's rules that I have to post the work that I have...

Homework Statement - A common inhabitant of human intestines is the bacterium Escherichia coli. A cell of this bacterium in a nutrient-broth medium divides into two cells every 20 minutes. The initial population of a culture is 63 cells. - (a) Find the relative growth rate. Homework...

Homework Statement y = x^(18x^-4) Homework Equations chain rule dy/dx a^x = a^x ln a The Attempt at a Solution first i used the second equation from above to get x^(18/x^4)*ln(x) then i use the chain rule to get x^(18/x^4)*ln(x)*(-72x^-5) the computer program i am using is...

Solving Exponential Equations SO CONFUSED ? Homework Statement I'm trying to solve problems like these a) 2(3y-2) = 18 b) 27(33x+1) = 3 c) 2x+2 - 2x = 48 d) 10z+4 + 10z+3 = 11 Homework Equations Laws of exponential values. The Attempt at a Solution b) 2(3y-2) = 18 6y-2 = 18...

Is there an approximation for exp(-k*L) with L large but finite??

Hi, I have a (markov chain) transition matrix X which I understand. In particular each row of this matrix sums to 1. I have used this transition matrix to construct it's generator, Y. I.e. Y is the continuously compounded transition matrix, X = exp(Y) X*X = exp(2Y), etc both X and Y...

I'm trying to find the laplace transform (if possible) of exp(-2r/a)r^2. --- I did integration by parts to check that the integral of exp(-2r/a)r^2 from 0 to infinity is a^3 / 4. but i cannot get the laplace transform to work out. the answer mathematica online gives would have to have the term...

Homework Statement how can i convert this : - 2 (cos pai / 4 + i sin pai / 4 ) to Cartesian , Polar and Exponential form ? Homework Equations z = ( a + i b) The Attempt at a Solution r= -2 tan inverse = pai/4 / pai/4 ?? Thank you very much for helping me out

Express -2(cos pai/4+i sin pai/4 ) in Cartesian , Polar and Exponential form ? how can i convert this : - 2 (cos pai / 4 + i sin pai / 4 ) to Cartesian , Polar and Exponential form ? Thank you very much

Homework Statement Let <d1,d2,d3...dN> be an odered set of samples from an exponential random variable with parameter lambda. Let <l1,l2,l3,...,lM> the same. Let Z = min<d1,d2,...,dN> --> Z is exp with parameter lambda*N Let U = min<l1,l2,...,lM> --> U is exp with parameter lambda*M...

I want to solve a first order differential equation on the form y'+y=e^{x} I want to separate the variables, but not sure how...Thanks!