b) \(\frac{4x}{x+2}-\frac{3x}{x-2}+\frac{12}{x^2-4}\)
\(=\frac{4x}{x+2}-\frac{3x}{x-2}+\frac{12}{\left(x-2\right).\left(x+2\right)}\)
\(=\frac{4x.\left(x-2\right)}{\left(x-2\right).\left(x+2\right)}-\frac{3x.\left(x+2\right)}{\left(x-2\right).\left(x+2\right)}+\frac{12}{\left(x-2\right).\left(x+2\right)}\)
\(=\frac{4x^2-8x}{\left(x-2\right).\left(x+2\right)}-\frac{3x^2+6x}{\left(x-2\right).\left(x+2\right)}+\frac{12}{\left(x-2\right).\left(x+2\right)}\)
\(=\frac{4x^2-8x}{\left(x-2\right).\left(x+2\right)}+\frac{-\left(3x^2+6x\right)}{\left(x-2\right).\left(x+2\right)}+\frac{12}{\left(x-2\right).\left(x+2\right)}\)
\(=\frac{4x^2-8x-3x^2-6x+12}{\left(x-2\right).\left(x+2\right)}\)
\(=\frac{x^2-14x+12}{\left(x-2\right).\left(x+2\right)}\)
Chúc bạn học tốt!
