(-x-1)÷(x²+2x+1)
=-(x+1)÷(x+1)²
=-1/(x+1)
(4-m²n²)÷(m²n²-4mn+4)
=(4-m²n²)/(m²n²-4mn+4)
=-(m²n²-4)/(m²n²-4mn+4)
=-(mn-2)(mn+2)/(mn-2)²
=-(mn+2)/(mn-2)