解：[a/(a2-b2) - 1/(a+b)]÷b/(b-a) = -[a/(a+b)(a-b)-(a-b)/(a+b)(a-b)] × (a-b)/b = -b/(a+b)(a-b) × (a-b)/b = -1/(a+b) 当a = 3，b = -2时原式= -1/(3 - 2) = -1
