Question

先化简再求值：a的平方-4分之a+2加a+2分之1,其中a=3

Answer 1

(a+2)/(a²-4)+1/(a+2)

=(a+2)/[(a+2)(a-2)]+1/(a+2)

=(a+2)/[(a+2)(a-2)]+(a-2)/[(a+2)(a-2)]

=2a/(a²-4)

当a=3时,原式=6/(9-4)=6/5