Least Squares Solution - Or is there?

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I have a problem that says to find the least squares solution to
\newcommand{\colv}[2] {\left(\begin{array}{c} #1 \\ #2 \end{array}\right)}<br /> K x = \colv{2}{2} for
K = \left(<br /> \begin{array}{cc}<br /> 1 &amp; 2\\<br /> 2 &amp; 4<br /> \end{array} \right). Then express the solution in the form x = w + z, where w is in the corange, and z is in the kernel.

Since the determinate of the matrix K will be zero, then there should be infinite least squares solutions since the kernel is non-zero, correct? When I try to find a solution by multiplying each side by K^T, I get no solution rather than infinite solutions. Specifically the sytem

\newcommand{\colv}[2] {\left(\begin{array}{c} #1 \\ #2 <br /> \left(<br /> \begin{array}{cc}<br /> 5 &amp; 10\\<br /> 0 &amp; 0 <br /> \end{array} \right) x = \colv{0}{10}

How can I find the least square of a matrix with determinate zero? Everything I know is based off the fact that the matrix will be invertible.

*My last matrix is messed up somehow, it should be the augmented matrix {{5,10 | 5},{0,0 | 10}}.
 
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Nevermind, I made a calculation error.
 
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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