Question #309049

Find Elementary matrices E1, E2 so that E2 E1 A = I2, where A = matrix(1 0 2 3) and I2 is the respective identity matrix


1
Expert's answer
2022-03-14T16:54:19-0400

Given thatA=[1023]Given \space that\\A = \begin{bmatrix}1 & 0 & \\2 & 3\end{bmatrix}

Find elementary Matrices E1 and E2 such that E2 E1 A = I

Start by eliminating the 2 in matrix A.

E1A=[1003] [abcd][1023]=[1003] [a+2b3bc+2d3d]=[1003]E_1A = \begin{bmatrix}1 & 0 & \\0 & 3\end{bmatrix}\\\space\\ \begin{bmatrix}a & b & \\c & d\end{bmatrix}\begin{bmatrix}1 & 0 & \\2 & 3\end{bmatrix} = \begin{bmatrix}1 & 0 & \\0 & 3\end{bmatrix}\\\space\\ \begin{bmatrix}a+2b & 3b & \\c+2d & 3d\end{bmatrix} =\begin{bmatrix}1 & 0 & \\0 & 3\end{bmatrix}


hence a=1; b= 0; c=-2 ; d= 1


Therefore E1 = [1021]\begin{bmatrix}1 & 0 & \\-2 & 1\end{bmatrix} [Answer]


Find E2 (since we know what E1A is)

[abcd][1003]=[1001] [a3bc3d]=[1001] \begin{bmatrix}a & b & \\c & d\end{bmatrix}\begin{bmatrix}1 & 0 & \\0 & 3\end{bmatrix} = \begin{bmatrix}1 & 0 & \\0 & 1\end{bmatrix}\\\space\\ \begin{bmatrix}a & 3b & \\c & 3d\end{bmatrix} = \begin{bmatrix}1 & 0 & \\0 & 1\end{bmatrix}\\\space\\

hence a= 1; b= 0; c= 0; d=13\frac{1}{3}


Therefore E2 = [10013]\begin{bmatrix}1 & 0 & \\0 & \frac{1}{3}\end{bmatrix} [Answer]

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