\(\dfrac{\left(x^2+a\right)\left(1+a\right)+a^2x^2+1}{\left(x^2-a\right)\left(1-a\right)+a^2x^2+1}\)
\(=\dfrac{x^2+ax^2+a+a^2+a^2x^2+1}{x^2-ax^2-a+a^2+a^2x^2+1}\)
\(=\dfrac{\left(x^2+ax^2+a^2x^2\right)+\left(a+a^2+1\right)}{\left(x^2-ax^2+a^2x^2\right)+\left(a^2-a+1\right)}\)
\(=\dfrac{x^2\left(1+a+a^2\right)+\left(a+a^2+1\right)}{x^2\left(1-a+a^2\right)+\left(a^2-a+1\right)}\)
\(=\dfrac{\left(x^2+1\right)\left(a^2+a+1\right)}{\left(x^2+1\right)\left(a^2-a+1\right)}\)
\(=\dfrac{a^2+a+1}{a^2-a+1}\)
=> Biểu thức không phụ thuộc vào giá trị biến x