a) $3x^{}-5=5.(x^{}+1)$
⇔ $3x^{}-5=5x^{}+5$
⇔ $3x^{}-5x^{}=5+5$
⇔ $2x^{}=10$
⇔ $x^{}=55$
b) $(x^{}-1)(2x^{}-3)=0$
⇔ \(\left[ \begin{array}{l}x^{}-1=0\\2x^{}-3=0\end{array} \right.\)
⇔ \(\left[ \begin{array}{l}x=1\\2x=-3\end{array} \right.\)
⇔ \(\left[ \begin{array}{l}x=1\\x=\frac{-3}{2}\end{array} \right.\)
c) $\frac{x-3}{x+3}-\frac{x+3}{x-3}=\frac{6x^{2}}{9-x^{2}}$
⇔ $\frac{(x-3)(x-3)}{(x+3)(x-3)}-\frac{(x+3)(x+3)}{(x-3)(x+3)}=\frac{6x^{2}}{(x-3)(x+3)}$
⇔ $(x^{}-3)(x-3)-(x+3)(x+3)=6^{2}$
⇔ $x^{2}-3x-3x+9-x^{2}-3x-3x-9=36$
⇔ $-12x^{}=36$
⇔ $x^{}=-3$
Chúc bạn học tốt!
