`ĐKXĐ: a>0; a\ne4; a\ne1`
`Q=(1/(\sqrt{a}-1)-1/\sqrt{a}):((\sqrt{a}+1)/(\sqrt{a}-2)-(\sqrt{a}+2)/(\sqrt{a}-1))`
`Q=(\sqrt{a}-(\sqrt{a}-1))/(\sqrt{a}(\sqrt{a}-1)):((\sqrt{a}+1)(\sqrt{a}-1)-(\sqrt{a}+2)(\sqrt{a}-2))/((\sqrt{a}-2)(\sqrt{a}-1))`
`Q=(\sqrt{a}-\sqrt{a}+1)/(\sqrt{a}(\sqrt{a}-1)):(a-1-a+4)/((\sqrt{a}-2)(\sqrt{a}-1))`
`Q=1/(\sqrt{a}(\sqrt{a}-1)):3/((\sqrt{a}-2)(\sqrt{a}-1))`
`Q=1/(\sqrt{a}(\sqrt{a}-1)).((\sqrt{a}-2)(\sqrt{a}-1))/3`
`Q=(\sqrt{a}-2)/(3\sqrt{a})`
Vây với `a>0; a\ne4; a\ne1` thì `Q=(\sqrt{a}-2)/(3\sqrt{a})`
