After several quadratic roots are transformed into the simplest quadratic roots, if the number of roots is the same, these quadratic roots are called similar quadratic roots. A quadratic radical cannot be called a similar quadratic radical, and at least two quadratic radicals can be called similar quadratic radicals. To judge whether several radicals are similar quadratic radicals, we must first simplify the number in the radical number and change the non-simplest quadratic radical into the simplest quadratic radical, and then judge.