(a+1分之1-a的平方-1分之a-2)除以a+1分之1
=1/(a+1)x(a+1)-(a-2)/(a+1)(a-1)x(a+1)
=1-(a-2)/(a+1)
=(a+1-a+1)/(a+1)
=2/(a+1)
=2/(√3+1)
=2(√3-1)/2
=√3-1