\(ĐK:x\ne\pm3\\ \dfrac{10}{x+3}-\dfrac{8x-36}{x^2-9}\\ =\dfrac{10}{x+3}-\dfrac{8x-36}{\left(x-3\right)\left(x+3\right)}\\ =\dfrac{10\left(x-3\right)}{\left(x-3\right)\left(x+3\right)}-\dfrac{8x-36}{\left(x-3\right)\left(x+3\right)}\\ =\dfrac{10x-30-8x+36}{\left(x-3\right)\left(x+3\right)}\\ =\dfrac{2x+6}{\left(x-3\right)\left(x+3\right)}\\ =\dfrac{2\left(x+3\right)}{\left(x-3\right)\left(x+3\right)}\\ =\dfrac{2}{x-3}\)
\(=\dfrac{10}{x+3}-\dfrac{8x-36}{\left(x-3\right)\left(x+3\right)}=\dfrac{10\left(x-3\right)-8x+36}{\left(x-3\right)\left(x+3\right)}=\dfrac{10x-30-8x+36}{\left(x-3\right)\left(x+3\right)}=\dfrac{2x+6}{\left(x-3\right)\left(x+3\right)}=\dfrac{2\left(x+3\right)}{\left(x-3\right)\left(x+3\right)}=\dfrac{2}{x-3}\)
\(\dfrac{8x-36}{x^2-9}=\dfrac{8x-36}{\left(x-3\right)\left(x+3\right)}\)
\(MTC:\left(x+3\right)\left(x-3\right)\)
\(\dfrac{10.\left(x-3\right)}{\left(x+3\right)\left(x-3\right)}=\dfrac{10x-30}{\left(x+3\right)\left(x-3\right)}\)
\(\dfrac{8x-36.\left(1\right)}{\left(x+3\right)\left(x-3\right)}=\dfrac{8x-36}{\left(x+3\right)\left(x-3\right)}\)
\(\dfrac{10x-30}{\left(x+3\right)\left(x-3\right)}-\dfrac{8x-36}{\left(x+3\right)\left(x-3\right)}\)
\(=\dfrac{\left(10x-30\right)-\left(8x-36\right)}{\left(x+3\right)\left(x-3\right)}\)
\(=\dfrac{10x-30-8x+36}{\left(x+3\right)\left(x-3\right)}\)
\(=\dfrac{2x+6}{\left(x+3\right)\left(x-3\right)}=\dfrac{2\left(x+3\right)}{\left(x+3\right)\left(x-3\right)}=\dfrac{2}{x-3}\)
