public static void subtractEquals( DMatrix2 a , DMatrix2 b ) {
        a.a1 -= b.a1;
        a.a2 -= b.a2;
    }
public static void subtractEquals ( DMatrix2 a , DMatrix2 b ) { a . a1 -= b . a1 ; a . a2 -= b . a2 ; }
<p>Performs the following operation:<br>
<br>
a = a - b <br>
a<sub>i</sub> = a<sub>i</sub> - b<sub>i</sub> <br>
</p>

@param a A Vector. Modified.
@param b A Vector. Not modified.