`Đặt \frac{10}{x^2+1}=k in ZZ,\text{ ta có:} kx^2+k=10 nên x^2=\frac{10-k}{k}`
`\text{Ta phải có}\frac{10-k}{k}>= 0 nên 0<k<=10.\text{ Ta có bảng sau:}`
\begin{array}{|c|c|c|}\hline \text{k}&\text{1}&\text{2}&\text{3}&\text{4}&\text{5}&\text{6}&\text{7}&\text{8}&\text{9}&\text{10}\\\hline \text{$x^{2}$=$\dfrac{10-k}{k}$}&\text{9}&\text{4}&\text{$\dfrac{7}{3}$}&\text{$\dfrac{3}{2}$}&\text{1}&\text{$\dfrac{2}{3}$}&\text{$\dfrac{3}{7}$}&\text{$\dfrac{1}{4}$}&\text{$\dfrac{1}{9}$}&\text{0}\\\hline \text{x $\in$ Q}&\text{$\pm$3}&\text{$\pm$2}&\text{}&\text{}&\text{$\pm$1}&\text{}&\text{}&\text{$\pm$$\dfrac{1}{2}$}&\text{$\pm$$\dfrac{1}{3}$}&\text{0}\\\hline \end{array}
`\text{Đáp số:}+-3,+-2,+-1,+-1/2,+-1/3,0`
