Question

Quy đồng mẫu các phân thức sau:

a) 1 phần x+2 và 8 phần 2x-x²

b) x²+1 và x² phần x²-1

Answer 1

a)

\(\dfrac{1}{x+2}=\dfrac{1}{2+x}\)

\(\dfrac{8}{2x-x^2}=\dfrac{-8}{-x\left(2+x\right)}=\dfrac{8}{x\left(2+x\right)}\)

MTC: \(x\left(2+x\right)\)

\(\dfrac{1}{x+2}=\dfrac{1}{2+x}=\dfrac{x}{x\left(2+x\right)}\)

\(\dfrac{8}{2x-x^2}=\dfrac{-8}{-x\left(2+x\right)}=\dfrac{8}{x\left(2+x\right)}\)

Answer 2

b)

\(x^2+1=\dfrac{x^2+1}{1}\)

\(\dfrac{x^2}{x^2-1}=\dfrac{x^2}{\left(x-1\right)\left(x+1\right)}\)

MTC: \(\left(x-1\right)\left(x+1\right)\)

\(x^2+1=\dfrac{x^2+1}{1}=\dfrac{\left(x-1\right)\left(x+1\right)\left(x^2+1\right)}{\left(x-1\right)\left(x+1\right)}\)

\(\dfrac{x^2}{x^2-1}=\dfrac{x^2}{\left(x-1\right)\left(x+1\right)}\)