Với `a >= 0,a \ne 1` có:
`C=([1-a\sqrt{a}]/[1-\sqrt{a}]+\sqrt{a})([1-\sqrt{a}]/[1-a])^2`
`C=([(1-\sqrt{a})(1+\sqrt{a}+a)]/[1-\sqrt{a}]+\sqrt{a})([1-\sqrt{a}]/[(1-\sqrt{a})(1+\sqrt{a})])^2`
`C=(1+\sqrt{a}+a+\sqrt{a})(1/[1+\sqrt{a}])^2`
`C=(1+2\sqrt{a}+a) . 1/[(1+\sqrt{a})^2]`
`C=(1+\sqrt{a})^2 . 1/[(1+\sqrt{a})^2]`
`C=1`