public function testRREFAlreadyComputed()
{
$A = new Matrix([[1, 2, 3], [2, 3, 4], [3, 4, 5]]);
$rref1 = $A->rref();
// computes rref
$rref2 = $A->rref();
// simply gets already-computed rref
$this->assertEquals($rref1, $rref2);
}
