Good pair
= Good pair
A pair $(X,A)$ is good when $A$ is closed and is a deformation retract of some neighborhood in $X$. Such a pair satisfies the hypotheses needed to compare relative homology with the reduced homology of a quotient.
= Good pair
A pair $(X,A)$ is good when $A$ is closed and is a deformation retract of some neighborhood in $X$. Such a pair satisfies the hypotheses needed to compare relative homology with the reduced homology of a quotient.