A method of extracting roots is to use the factorization of a number (by successively dividing out primes until the number is manageable) factoring 324... 324=2*162= 2^2*81=2^2*9^2
so that 324 = (2*9)^2 = 18^2
therefore the square root of 324 is 18 ±√324 = ±18 :)