I think that the absolute value of the determinant is the enlargement factor of a matrix. So if ad-bc is 2.2-0.0 the factor is 4. Is that correct?
A question says "Obtain the 2 × 2 matrix M associated with an enlargement, scale factor 2." I think that the a and d elements must be the square root of 2. Why does the answer say they are 2?
The determinant of a matrix gives you the area represented by the matrix, not the scale factor of enlargement. An enlargement of scale factor M is defined as
This can be shown quite easily. Take a general point x,y.
Now apply the transformation:
Edit: Was beaten by HallsofIvy