1. T

    Help me with the proof in a tetrahedron - my (wrong) solution attached

    I have got a problem I can't solve myself. I had an attempt, but it's wrong. I was told to draw a grid of this tetrahedron and then it's easier to find a solution (I tried it, but I don't see anything). There is a tetrahedron (ABCD), where $$\angle{ACB}=\angle{ADB}=90^\circ $$ and $$ AC=CD=DB...
  2. D

    Groups, whether law is right or wrong

    I dont know witch forums it's belong so..if it wrong please move it i need to say if that 2 sentenses if right or wrong and prove it plesae help me file attach. thanks
  3. T

    Im I wrong or is the answer not available

    Iv tried multiple times and I cant get an answer that is listed. What gives?
  4. maxpancho

    Related rates problem, not sure what's wrong

    A road running north to south crosses a road going east to west at the point P. Car A is driving north along the first road, and airplane B is flying to the east of P at an altitude of 2 km. At a particular time car A is 10 kilometers to the north of P and traveling at 80 km/hr, while airplane B...
  5. M

    Where did i go wrong?

    I have a problem that look like this: cos(3x)=1/ sqrt2 I already got the correct anser but my teacher says i have to give a more detailed description of how i solved it and he says that part of calculatón is wrong, this is my calculation: The unit circle value for the equation above is 40...
  6. B

    Easy compactness proof, What is wrong with my picture/logic?

    Theorem. If {Kα} is a collection of compact subsets of a metric space X such that the intersection of every finite subcollection of {Kα} is nonempty, then ∩Kα is nonempty. Proof. Fix a member K1 of {Kα} and put Gα=Kcα [this denotes the complement of Kα]. Assume that no point of K1 belongs...
  7. K

    Why am I getting this wrong?

    I am going to soon be writing a math test to upgrade my high school grades for a college course in Canada. Here is my question that I need help solving. More than anything, I need to see the steps involved in solving. I already know the answer is 2. Thanks so much!
  8. K

    does wolfram give wrong answer?

    1. laplace transform unitstep(t-2)*(t-2)^2 laplace transform unitstep(t-2)*(t-2)^2 - Wolfram|Alpha the correct answer is (2e^-(2s))/s^3 2.solving some system of linear differential equation also gives wrong answer y'=y-x , x'=y+3x - Wolfram|Alpha correct answer is y(t)= e^2t...
  9. N

    What's wrong with the following proof? (Strong induction)

    Statement: For any integer n\geq 0, (x^n)'=0 Proof Base Case: For n=0, x^0=1, so \, (x^0)'=(1)'=0 Induction hypothesis: Assume that for some k, (x^i)'=0 for all 0 \leq i \leq k Induction step: Consider x^{k+1} . Note that x^{k+1} = x* x^k Using product rule...
  10. T

    Sum of series .. keep getting wrong answer

    Hello, Question : Find the sum of the convergent series ( (1/e)^n + ( 1 / n(n+1) ) ) from n=1 to n=infinity Clearly, the series is a sum of two convergent series First series is geometric series with sum = a / (1-r) = 1 / ( 1 - (1/e) ) = e / (e-1) Second series is telescoping series with Sn =...
  11. K

    What did I do wrong on this integral?

    Hi, I have an integral $\int \frac{6x^3}{x^3+1}$. First thing I do is long division to get $\int 6 - \int \frac{6}{x^3+1}$. To solve the second integral, I expand the denominator using the sum of cubes rule and then use partial fraction decomposition and find that A = 2, B = 2, and C = 4. This...
  12. B

    I keep getting it wrong! help!

    Estimate the area under the graph of f(x) = 2 x from x = 0 to x = 4 using four approximating rectangles and right endpoints. (Round your answers to four decimal places.)
  13. romsek

    Latex Test - Is the new LaTex running? What am I doing wrong?

    $$\left(\begin{array}{c}&0 \\ &1 \end{array}\right)$$ $$\sqrt{3}$$ $$1 ~,~ \sqrt 2 ~,\&~ \sqrt {\frac{3}{2}}$$
  14. sakonpure6

    Am I wrong?

    Can some one please check my answer for question 7, I have a quiz tomorrow and I want to make sure I understand!!
  15. D

    Finding a counterexample to wrong derivatives

    Hello Forum, I find this problem to be extremely difficult. Any help is appreacited! Each of the following "derivatives" has been done incorrectly. In each case below, find a counterexample, that shows why the reasoning is incorrect. Then correct the mistakes by finding the actual derivatives...
  16. R

    What did I do wrong on this implicit differentiation problem

    Im supposed to find the slope of the tangent line at the point (3,2) for the function (4x^2+2y^2)^2-4x^2y=1864 So here's what I did 2(4x^2+2y^2)(8x+4yy')-4(2xy+x^2y')=0 (8x^2+4y^2)(8x+4yy')-8xy-4x^2y'=0 64x^3+32x^2yy'+32y^2x+16y^3y'-8xy-4x^2y'=0 y'(32x^y+16y^3-4x^2)=-64x^3-32y^2x+8xy...
  17. S

    Why is this trollmath wrong?

    Hi forum, I saw this trollmath on youtube. i dont claim its correct, but i cant understand where the mistake is. help :) Consider a geometric series as follows: S = 2 + 4+ 8 + 16 + ...... [1] 2S = 4 + 8+ 16 + ...... [2] [2]-[1] S = 2 Clearly the last line is false, but where...
  18. H

    Limit problem (what's going wrong?)

    {\lim _{x \to - \infty }}{\frac{4x}{\sqrt{x^{2}+4x}+x}}} This gives - \infty, which is correct. Dividing both the numerator and the denominator by x, we have {\lim _{x \to - \infty }}{\frac{4}{\sqrt{1+\frac{4}{x}}+1}}} now this gives me 2. What's wrong? P.S. I tested the values on a...
  19. H

    Limit problem (what's going wrong?)

    {\lim _{x \to - \infty }}{\frac{4x}{\sqrt{x^{2}+4x}+x}}} This gives - \infty, which is correct. Dividing both the numerator and the denominator by x, we have {\lim _{x \to - \infty }}{\frac{4}{\sqrt{1+\frac{4}{x}}+1}}} now this gives me 2. What's wrong? P.S. I tested the values on a...