(b+1)/(a²-4)÷(b²+b)/(a+2)
=(b+1)/[(a-2)(a+2)]×(a+2)/[b(b+1)]
=1/[b(a-2)]
(x²-1)/(x²+4x+4)×1/(x+1)×[(x+1)(x+2)]/(1+x)
=(x-1)(x+1)/(x+2)²×1/(x+1)×[(x+1)(x+2)]/(1+x)
=(x-1)/(x+2)
(b+1)/(a²-4)÷(b²+b)/(a+2)
=(b+1)/[(a-2)(a+2)]×(a+2)/[b(b+1)]
=1/[b(a-2)]
(x²-1)/(x²+4x+4)×1/(x+1)×[(x+1)(x+2)]/(1+x)
=(x-1)(x+1)/(x+2)²×1/(x+1)×[(x+1)(x+2)]/(1+x)
=(x-1)/(x+2)