sqrt(a^2sqrt(a^4,5),7)/sqrt(a,5)
7√a2×5√a45√a
=7√a2×a4∗(1/5)a1/5=7√a2×a0.8a0.2=7√a2.8a0.2=(a2.8)1/7a0.2=a2.8/7a0.2=a0.4a0.2=a0.4−0.2=a0.2=a1/5=5√a