先化简再求值(a^2-b^2/a^2b-ab^2)^-2*91+a^2+b^2/2ab)其中a=6,b=-39=（

先化简再求值(a^2-b^2/a^2b-ab^2)^-2*91+a^2+b^2/2ab)其中a=6,b=-3
9=（

原式=[(a+b)(a-b)/ab(a-b)]^(-2)*(2ab+a²+b²)/2ab
=a²b²(a-b)²/(a+b)²(a-b)²*(a+b)²/2ab
=a²b²/(a+b)²*(a+b)²/2ab
=ab/2
=6×(-3)/2
=-9

(a^2-b^2/a^2b-ab^2)^-2*(1+a^2+b^2/2ab)
=[ab(a-b)/(a+b)(a+b)]²×(a+b)²/2ab
=a²b²/(a+b)² ×(a+b)²/2ab
=ab/2
当a=6 ，b=-3时
原式=-9