Jacobi Iteration Homework: Solving System of Equations

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Homework Statement



consider the systems of equations
2x1 - x2 = 1
-31 + 4x2 =11

a) determine the ixact solution?

b)apply jacobi iteration.Does the matrix C satisfy the required condition?

c)starting with x(0) =( \stackrel{1}{1} ) calculate x(1) and x(2) and the prior error bound for x(2)

d)how many iterations will suffice to get within 0.001 of the solution?

a) grand 3 and 5
b) it clearly satisfies the condition as off diagonals < diagonals
c) so did it out got
x(0) = ( \stackrel{1}{14/4} )

x(1) = ( \stackrel{18/8}{14/4} )

x(2) = ( \stackrel{18/8}{71/16} )

but now I am not sure what is meant by prior error bound, compare with the actual error?

d) do i just keep doing it out till i get within .001? (aghhhhh)
 
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but now I am not sure what is meant by prior error bound, compare with the actual error?

It's the error estimate that can be obtained before the actual iteration's calculus. There's an expression for it in terms of the matrixes.

do i just keep doing it out till i get within .001?

No. You use the expression for the a priori error (it depends on n) to find n.
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
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