Question

можете помочь? я не могу решить.

Answer 1

Ответ:

$\dfrac{6x^{2}}{x^{2}-9};$

$\dfrac{-4c}{c^{2}-16};$

Объяснение:

$\dfrac{3x}{x+3}+\dfrac{3x}{x-3}=\dfrac{3x(x-3)+3x(x+3)}{(x+3)(x-3)}=\dfrac{3x^{2}-9x+3x^{2}+9x}{x^{2}-3^{2}}=\dfrac{6x^{2}}{x^{2}-9};$

$\dfrac{c}{c+4}-\dfrac{c^{2}}{c^{2}-16}=\dfrac{c}{c+4}-\dfrac{c^{2}}{c^{2}-4^{2}}=\dfrac{c}{c+4}-\dfrac{c^{2}}{(c-4)(c+4)}=\dfrac{c(c-4)-c^{2}}{(c-4)(c+4)}=$

$=\dfrac{c^{2}-4c-c^{2}}{c^{2}-16}=\dfrac{-4c}{c^{2}-16};$