Question

 помогите сократить дробь 

Answer 1

$(a-9a^{1/2})/(7a^{1/4}+21)=a^{1/2}(a^{1/2}-9)/7(a^{1/4}+3)= \ a^{1/2}(a^{1/4}-3)(a^{1/4}+3)/7(a^{1/4}+3)=a^{1/2}(a^{1/4}-3)/7$