Упростите выражение 5a-3/5a-4*(5a -  5a/5a-3)

[latex] \frac{5a-3}{5a-4}(5a - \frac{5a}{5a-3} )= \frac{5a-3}{5a-4}\cdot \frac{5a(5a-3)-5a}{5a-3}= \frac{5a-3}{5a-4}\cdot \frac{25a^2-15a-5a}{5a-3}= \\\ = \frac{5a-3}{5a-4}\cdot \frac{25a^2-20a}{5a-3}= \frac{(5a-3)(25a^2-20a)}{(5a-4)(5a-3)}= \frac{5a(5a-4)}{5a-4}=5a[/latex]