81-x^2/x^2+6x+9/x-9/2x+3*a+3/a+9
问题描述:
81-x^2/x^2+6x+9/x-9/2x+3*a+3/a+9
答
=-(x+9)(x-9)/(x+3)^2 ×(2x+3)/(x-9)×(x+3)/(x+9)
=-(2x+3)/(x+3)