1 | initial version |

Since you know that the variables are `x`

and `y`

,
grab their coefficients in each entry of `A`

.

Use list comprehension to build a list of lists out of that.

Then create a matrix from this list of list.

The variables:

```
sage: x, y = SR.var('x, y')
```

The matrix `A`

:

```
sage: A = matrix([[x], [x - 2*y]])
sage: A
[ x]
[x - 2*y]
```

The vector of variables:

```
sage: b = matrix([[x], [y]])
```

The matrix of coefficients:

```
sage: C = matrix([[e.coefficient(x), e.coefficient(y)] for row in A for e in row])
```

Check:

```
sage: C, b, C*b, A
(
[ 1 0] [x] [ x] [ x]
[ 1 -2], [y], [x - 2*y], [x - 2*y]
)
```

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