x-2分之根号x-2除以根号x的三次方-2x的平方分之根号x
=[√(x-2)]/(x-2)÷[√x/x√(x-2)]
=[1/√(x-2)]*[x√(x-2)/√x]
=x/√x
=√x
当x=9,
原式=√x=√9=3