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
