Ta có: \(\frac{a+x}{a^2x}+\frac{x+b}{x^2b}+\frac{b+a}{b^2a}\)
\(=\frac{b^2x\left(a+x\right)}{a^2b^2x^2}+\frac{a^2b\left(x+b\right)}{a^2b^2x^2}+\frac{x^2\cdot a\left(b+a\right)}{a^2b^2x^2}\)
\(=\frac{ab^2x+b^2x^2+a^2bx+a^2b^2+x^2\cdot ab+x^2\cdot a^2}{a^2b^2x^2}\)