a. \(\dfrac{x}{x-3}+\dfrac{9-6x}{x^2-3x}\)
\(=\dfrac{x}{x-3}+\dfrac{9-6x}{x\left(x-3\right)}\)
\(=\dfrac{x^2+9-6x}{x\left(x-3\right)}\)
\(=\dfrac{\left(x-3\right)^2}{x\left(x-3\right)}=\dfrac{x-3}{x}\)
b. \(\dfrac{x+2}{3x}+\dfrac{x-5}{5x}-\dfrac{x+8}{4x}\)
\(=\dfrac{20\left(x+2\right)+12\left(x-5\right)-15\left(x+8\right)}{60x}\)
\(=\dfrac{20x+4x+12x-60-15x-120}{60x}\)
\(=\dfrac{21x-180}{60x}=\dfrac{3\left(7x-60\right)}{60x}=\dfrac{7x-60}{20x}\)
c. \(\dfrac{-4x+6}{2x-2}+\dfrac{-2x}{1-x}\)
\(=\dfrac{-4x+6}{2\left(x-1\right)}+\dfrac{2x}{x-1}\)
\(=\dfrac{-4x+6+4x}{2\left(x-1\right)}\)
\(=\dfrac{3}{x-1}\)
dạng như v bạn chỉ cần làm xuất hiện mẫu chung là dc
