Сразу решение : 1) a/b(a-4b)/4a^2/(a-4b^2)=a/b(a-4b)*(a-4b)^2/4a^2=a*(a-4b)^2/b(a-4b)4a^2=a-4b/4ab
2)a/b(a=2b)/4a^2/(a=2b)^2=a*(a=2b)^2/b(a=2b)4a^2=a=2b/4ab
3)a/b(a+6b)/3a^2/(a+6b)^2=a*(a+6b)^2/b(a+6b)*3a^2=a+6b/3ab
4)a/b(a-5b)/5a^2/(a-5b)^2=a*(a-5b)^2/b(a-5b)*5a^2=a-5b/5ab
дальше сама