Sunday, September 22, 2013

Calculus II for Bio

Ask a math question of medium difficulty. Try looking through some and see if you can work out the answers. You'll need a writing utensil and some paper. Don't be lazy.

Here are two problems to get things started:
(Without looking in your book) Give an example of two $2\times 2$ matrices which do not commute.

If there was a $2\times 2$ matrix $A$ such that $A \cdot B = B \cdot A $ for all $2\times 2$ matrices $B$, what does $A$ look like?

30 comments:

  1. Interpret the following Leslie Matrix.
    0 5 2.5 0
    .8 0 0 0
    0 .5 0 0
    0 0 .1 0
    Then find the next three population vectors if the starting population N0(t) is 1000, the next generation at the start of the breeding season is N1(t)=800, the start of the next breeding season is N2(t)=500, and the start of the next breeding season is N3(t)=100

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    Replies
    1. Interpret the following Leslie Matrix.
      $\begin{bmatrix} 0 &5 &2.5& 0\\
      .8& 0& 0& 0\\
      0 &.5 &0& 0\\
      0& 0& .1& 0 \end{bmatrix}$
      Then find the next three population vectors if the starting population $N_0(t)=1000$, the next generation at the start of the breeding season is $N_1(t)=800$, the start of the next breeding season is $N_2(t)=500$, and the start of the next breeding season is $N_3(t)=100$
      (see example 17 in section 9.2 on page 462 )

      Delete
  2. A is represented by the Matrix
    5 6
    7 10
    and B is represented by the Matrix
    8 9 13 12
    6 3 10 -8
    If AX=B solve for the Matrix X.

    Next keep B the same but change A to the matrix
    3 6
    2 4

    ReplyDelete
    Replies
    1. $A$ is represented by the matrix $\begin{bmatrix} 5 &6 \\ 7 &10\end{bmatrix}$
      and $B$ is represented by the matrix $\begin{bmatrix} 8& 9& 13& 12\\ 6& 3& 10& -8\end{bmatrix}$
      Is there a solution to $AX=B$, if so, solve for the matrix $X$.

      Next keep $B$ the same but change $A$ to the matrix
      $\begin{bmatrix} 3& 6 \\ 2 &4 \end{bmatrix}$.
      Is there a solution to $AX=B$, if so, solve for the matrix $X$.

      Delete
  3. Find the inverse of the 2x2 matrix B if B equals:

    2 4
    1 4

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  4. What is the determinant of this 3x3 matrix?

    3 4 1
    6 8 2
    5 7 9

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  5. If $\left| \vec{x} \right| = 5$, what is the length of $-3 \vec{x}$?

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  6. Find the values of x, y, and z that satisfy all three equations:

    3x + 5y - z = 10
    2x - y + 3z = 9
    4x + 2y - 3z = -1

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  7. Find A^2 x C' for the following matrices

    A= 2 5 B= 1 4 C= 6 2
    3 8 7 4 5 3
    4 1

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    Replies
    1. Given $A= \begin{bmatrix}2& 5\\3&8\end{bmatrix}$ $B= \begin{bmatrix}1 &4\\7&4\end{bmatrix}$ $C= \begin{bmatrix}6& 2\\5&3\end{bmatrix}$, determine $A^2 C$.

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  8. Given the following matrix A, find its eigenvalues and corresponding eigenvectors.

    4 3
    1 5

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  9. Show that AB =/= BA if
    A=
    3 5
    -3 2

    and

    B=
    5 9
    2 -1

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    Replies
    1. Given $A=\begin{bmatrix} 3 & 5\\ -3 & 2 \end{bmatrix}$ and $B=\begin{bmatrix} 5&9\\2&-1 \end{bmatrix}$, show that $AB \neq BA$.

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  10. Laboratory mice are fed with a mixture of two foods that contain two essential nutrients. food 1 contains 3 units of nutrient A and 2 units of nutrient B per ounce; food 2 contains 4 units of nutrient A and 5 units of nutrient B per ounce. In what proportion should you mix the food if the mice require nutrients A and B in equal amounts?

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  11. Show that (AB)' does not equal A'B'

    Let A = 4 1 3
    0 1 2
    1 0 0

    Let B= 1 0 1
    2 3 1
    5 1 0

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  12. Find the inverse of the following 3x3 matrix:
    9 4 1
    A= 0 2 3
    5 8 0

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  13. find [ A^-1 + B ] C
    Where:
    A=2 5
    7 5

    B= 3 1
    2 5

    C=1 0
    3 0

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  14. Find the eigenvalues and eigenvectors for the following matrix:
    A= [3 6]
    [2 8]

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  15. Find the eigenvalues of matrix (AB)'
    Where
    A = [7 5 ]
    6 9

    B = [3 5]
    5 1

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  16. find and classify the equlibria points when dy/dx = X^3+4x^2+2x

    ReplyDelete
    Replies
    1. I will adjust this problem to being:
      Find and classify the equilibria to
      $\frac{dy}{dx}=y^3+4y^2+4y$

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  17. Vector A and Vector B are represented by the Cartesian system as (3, 4) and (1/2, 3) respectively. The vectors are added. Define Vector(A+B) using polar coordinates.

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  18. ANSWER THESE QUESTIONS:
    Normalize this vector: [1, 5, 12]
    Find the dot product of (2, 1) (5, 6)
    Find the angle between these 2 lines: x = [-1,2]' y = [-2,-4]'
    -Seal-Bin Han

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  19. Replies
    1. Everyone should know how to do this.
      Compute $A^{12} x$ where $A=\begin{bmatrix} 2&3\\1&4\end{bmatrix}$ and $x=\begin{bmatrix} 6\\ 4\end{bmatrix}$

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  20. Find [A+B]^-1
    when A= 5 7
    2 4
    and B = 2 1
    3 4

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  21. Calculate the value of the following integral with the bounds of negative infinity to positive infinity ∫ (1/(x^2 -1) dx

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    Replies
    1. Does $\int_{-\infty} ^{\infty} \frac{1}{x^2-1}dx$ exist?

      Delete
  22. Find the eigenvalues and eigenvectors for martrix G.

    G=
    [3 6]
    [2 4]

    ReplyDelete