Question

81-a的平方/a的平方+6a+9除以a-9/2a+6乘以a+3/a+9

Answer 1

81-a的平方/a的平方+6a+9除以a-9/2a+6乘以a+3/a+9

=(9+a)(9-a)/(a+3)^2÷(a-9)/2(a+3)×(a+3)/(a+9)

=-(9+a)(a-9)/(a+3)^2×2(a+3)/(a-9)×(a+3)/(a+9)

=-2