Matrix.inverse

import std.math : approxEqual;
auto m1 = Matrix2D(2.0, 3.0, /**/ -1.0, 5.0);
auto m2 = m1.inverse();
assert (m2.v[0].approxEqual(0.384615));
assert (m2.v[1].approxEqual(-0.230769));
assert (m2.v[2].approxEqual(0.0769231));
assert (m2.v[3].approxEqual(0.153846));