Упростите выражение под номером 5

Решите задачу:

$(\frac{b^{1,5}+2}{b^{2,5}-2b^2}-\frac{b^{1,5}-2}{b^{2,5}+2b^2})*\frac{b-4}{b^{1,5}}=\\\\=\frac{(b^{1,5}+2)*(b^{2,5}+2b^2)-(b^{1,5}-2)*(b^{2,5}-2b^2)}{(b^{2,5}-2b^2)*(b^{2,5}+2b^2)}*\frac{b-4}{b^{1,5}}=\\\\=\frac{b^{4}+2b^{2,5}+2b^{3,5}+4b^2)-(b^{4}-2b^{2,5}-2b^{3,5}+4b^2)}{(b^{2,5}-2b^2)*(b^{2,5}+2b^2)}*\frac{b-4}{b^{1,5}}=\\\\=\frac{b^{4}+2b^{2,5}+2b^{3,5}+4b^2-b^{4}+2b^{2,5}+2b^{3,5}-4b^2}{(b^{2,5}-2b^2)*(b^{2,5}+2b^2)}*\frac{b-4}{b^{1,5}}=$

$=\frac{4b^{2,5}+4b^{3,5}}{(b^{2,5}-2b^2)*(b^{2,5}+2b^2)}*\frac{b-4}{b^{1,5}}=\\\\=\frac{4b^{2,5}*(1+4b)}{(b^{2,5})^2-(2b^2)^2}*\frac{b-4}{b^{1,5}}=\\\\=\frac{4b^{2,5}*(1+4b)}{b^{5}-4b^4}*\frac{b-4}{b^{1,5}}=\\\\=\frac{4b^{2,5}*(1+4b)}{b^{4}*(b-4)}*\frac{b-4}{b^{1,5}}=\\\\=\frac{4b^{2,5-1,5}*(1+4b)}{b^{4}}=\frac{4b*(1+4b)}{b^{4}}=\frac{4(1+4b)}{b^{3}}$