Bạn tham khảo:
a) ${\dfrac{1-2x}{6x^3y}+\dfrac{3+2y}{6x^3y}+\dfrac{2x-4}{6x^3y}}$
= ${ \dfrac{1-2x+3+2y+2x-4}{6x^3y}}$
= ${ \dfrac{ 2y}{6x^3y}}$
= ${ \dfrac{1}{3x^3}}$
b) ${\dfrac{x^2-2}{x.(x-1)^2}+\dfrac{2-x}{x.(x-1)^2}}$
= ${ \dfrac{ x^2-2+2-x}{x.(x-1)^2}}$
= ${\dfrac{ x^x-x}{x.(x-1).(x-1)}}$
= ${ \dfrac{x.(x-1)}{x.(x-1).(x-1)}}$
= ${ \dfrac {1}{x-1}}$
c) ${\dfrac{3x+1}{x^2-3x+1}+\dfrac{x^2-6x}{x^2-3x+1}}$
= ${ \dfrac{3x+1+x^2-6x}{x^2-3x+1}}$
= ${ \dfrac{ x^2-3x+1}{x^2-3x+1}}$
= ${1}$
