Math Is Fun Forum

(a)   Consider a system of equations below, 
      

   

   

    Apply Gauss Elimination method to determine the values of x1, x2 and x3.
     
(b)    Use Cramer’s rule to solve the following simultaneous equations.
       

   

   

    Express the values of x, y and z in terms of r, s and t.

I have been trying to solve these two questions but I stuck, especially the first one.

How I did (a):

                     

          Row2 - 2Row1
                     

           Row3 - 4Row1

    then i get 

                   

                   

and here is where I stuck. I just learned these two rules yesterday.

1. 3x3 matrix question.
                                                         2, s, t
Determine the value of 3s+t when A=  2, 0, s+t   is a symmetric matrix.
                                                        3, 3, t

1.
a.)    Your instructor gives the class a surprise four-question with 3-choice quiz. You have not studied the material being quizzed and therefore decide to answer the four questions by randomly guessing the answers without reading the questions or the answers.
Calculate
i)    what is the probability that you have more than half of the answers correct?
ii)    what do you think the class “average” number of correct answers will be, if an entire class answers the quiz by guessing ?

b)    The incomes of senior executive in a large corporation are normally distributed with a standard deviation of RM 1200. A cutback is pending, at which time those who earn less RM 28,000 will be discharged. If such a cut represents 5% of the junior executives, what is the current mean salary of the group of senior executives?

Many experts predicted that BN would gain control of the executive branch of the federal government in the year 2013 election. At one time, the general consensus among political scientists was that if BN fielded their best presidential candidate, they would have a 65% chance of winning the 2013 election. In addition, a poll of several thousand voters from across the nation indicated that 54% intended to vote BN.

Revise the experts’ opinion in light of the information from the poll using a Bayesian tabular analysis.