backwards

  1. O

    Row echelon form backwards?

    x=1-2*t y=-2+3*t z=t Find a system of linear equations that has S as its solution set - don't make it too trivial - and explain what you are doing. Then show that solution with all steps clearly explained
  2. X

    Working backwards

    Hi guys Assume we have a random number generator (RNG) that we will run twice. We do not know exactly what range of numbers the RNG will select from, but we know that if we run it twice we have an overall chance of 1 in 512 of hitting the 'lucky' number. What is the probability of of hitting...
  3. F

    Working Backwards with Simultaneous Equations

    I am currently studying simultaneous equations, but there is a particular type of problem that I cannot figure out. For example: In a money bank there is £11.40, made up of 35 coins. All the coins are either 30ps or 50ps. The example is just made up, but how would you work this out using...
  4. A

    Backwards intergration

    \int\!\frac{1}{(1+x^2)^2}dx where x = tan u and u = arctan x I can't see where acrtan has come from. What part of the integrand is arctan?
  5. L

    Rotation of Ellipse to FIND the Bxy term, from horizontal to an angle of pi/4

    In essence I'm trying to take a horizontal ellipse and put it at an angle, rotating it around the origin. It's for my conics project, I'm making the elliptical orbits of the planets. So I have the a, b, and c terms of the ellipse, (as in the distance from vertice to center and such) which are...
  6. K

    Simplex algorithm, working backwards, help asap!

    The problem is implementing the simplex algorithm. I am given the final tableau and need to work backwards to find the original coefficients of the optimal objective value. In other words, I am given ONLY a final, optimal tableau and need to somehow get from it the optimal objective function...
  7. M

    Working backwards with percentages

    There is one type of question to do with percentages that I just can't get my head around. Below is an example: Staff at a computer game store get a discount of 21% on games. Bill bragged to his parents that he saved $102 last year. How much did Bill spend last year on games? I have been given...
  8. C

    Backwards Differentiation Formula

    How do I show the 2-step backwards differentiation formula is stable? ie. w2 -(4/3)w1 + (1/3)w = h*(2/3)f1
  9. billym

    Correct but backwards?

    I'm trying to find the points on x^2+8xy+7y^2=225 which are nearest the origin. Let: D^2=f(x,y)=x^2+y^2 g(x,y)=x^2+8xy+7y^2-225=0 So: f_x+\lambda g_x=0\Longrightarrow 2x+\lambda(2x+8y)=0 \Longrightarrow \lambda = -\frac{x}{x+4y} f_y+\lambda g_y=0\Longrightarrow 2y+\lambda(8x+14y)=0...
  10. V

    Working backwards to get level of significance?

    Hello all, I am familiar with tables such as this for determining the level of significance, given a certain df and R value. However, I have been searching high and low for the equation used to get these numbers with no luck. I am trying to figure out what my level of significance would be...
  11. L

    chain rule backwards?

    I have searched high and low and cannot find a problem in my text or online that seems to fit the format of the following question. I honestly get a bit confused with df/dx = df/du * du/dx anyway and this problem isn't helping. Here it is: Given that d/dx(f(2x^2)) = 7x^2 , find a formula for...
  12. A

    I can't seem to make Euclidean work backwards either. :/

    Use the extended Euclidean algorithm to find 198^-1 mod 257. Here's what I have: 257 = 198 x 1 + 59 198 = 59 x 3 + 21 59 = 21 x 2 + 17 21 = 17 x 1 + 4 17 = 4 x 4 + 1 Backwards: 1 = 17 - 4 x 4 1 = 17 - 4 (21 - 17) 1 = 5 x 17 - 4 x 21 1 = 5 x (59 - 21 x 2) - 4 x 21 I worked a little more and...
  13. C

    Euclidean Algorithm--can't seem to make it work backwards

    I'm working a problem in my textbook and am stuck. Here's what I have so far: GCD (34, 58) 58 = 34 x 1 + 24 34 = 24 x 1 + 10 24 = 10 x 2 + 4 10 = 4 x 2 + 2 = GCD (4, 2) So working backwards: 2 = 10 - 4 x 2 = 10 - (24 - 10 x 2) x 2 = 10 x 2 - 24 + 10 x 2 = 10 x 4 - 24 = (34 - 24) x...
  14. T

    Z-tables, Backwards and Interpolation: I just don't get it.

    I swear, every time I think I get it, I end up being completely wrong. Basically, I'm still confused as to how Z_{0.01}=2.326, or Z_{0.025}=1.96, or this: How did z_{a/2} become 2.575? I understand that 1-a=0.99 a=0.01 a/2=0.005 ...but not how that transforms into 2.575. (Worried)
  15. T

    Looking up Z-table "backwards"??

    Terribly stuck! How does one read a z-table 'backwards'?! In one question, I'm required to find a value z*, such that P(Z<z*)= 0.98 and P(0<Z<z*)= 0.48 -- by reading the table 'backwards'. And in the next one, in order to find z_{a/2}, I need to do the same. Any help would be greatly...
  16. K

    Working backwards

    if the total of a bill including GST came to 56.70 and GST is 6% what was the amount of the bill before GST was added? please show how u got this, thanks.
  17. B

    backwards Normal distribution problem

    I feel like I should be able to do this but I feel absolutely lost. Assume that the weight, X, of male college students is normally distributed. Assume further that P(X <= 160) = 1/2 and P(X <= 140) = 1/4. a.) What find the value of 'mu' and 'sigma' b.) Calculate P(X >= 190) c.) Calculate...
  18. T

    Backwards Derivative Rules

    I came up with two problems which I find interesting. 1)If f(x)+g(x) is differenciable at c, and f(x) is differenciable at c then is g(x) differenciable at c? 2)If f(x)g(x) is differenciable at c, and f(x) is differenciable at c then is g(x) differenciable at c?
  19. T

    Backwards Chain Rule

    I am too lazy to search for counter examples if somebody can find one that would be excellent. More excellent if he can proof it. Let f be a differenciable function at c and let g be a function which is defined on an open interval containing f(c) such that (g o f) is differenciable at c...
  20. C

    Backwards derivative problem

    Before, I posted a problem about partial derivatives. Well, this time I have to use the partial derivative to find F(x,y), and I'm not really sure how to go about it. I am given the two following partial derivatives. (1) The derivative of F with respect to x is x^2 divided by y and (2) The...