x^2-x/x+1÷x/x+1 ；x^2+6x+9/x^2-9÷x+2/x-3；2/a÷4/a

题目

x^2-x/x+1÷x/x+1 ；x^2+6x+9/x^2-9÷x+2/x-3；2/a÷4/a

答案

解1：原式=x(x-1)/(x+1)*(x+1)/x
=x-1
解2：原式=(x+3)^2/(x+3)(x-3)*(x-3)/(x+2)
=(x+3)/(x-3)*(x-3)/(x+2)
=(x+3)/(x+2)
解3：原式=2/a*a/4
=1/2