How to calculate gene frequencies?

If 0.16 are - - , the frequency of the - allele is sqrt(0.16) = 0.4. According to Hardy-Weinberg equation #1, the frequency of the + allele is 1 - 0.4 = 0.6. According to equation #2, the frequency of (+ -) = 2(0.6)(0.4) = 0.48