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Let $X$ be the $2$-sphere with two pairs of points identified, say $(1,0,0) \sim (-1,0,0)$ and $(0,1,0) \sim (0,-1,0)$. Write $Y$ for the wedge sum of two circles with a $2$-sphere: if it matters, the sphere is in the "middle," so the circles are attached at two distinct points on the sphere.

Now I think one can show, using Mayer-Vietoris and van Kampen, that these spaces have the same homology (that of a torus) and fundamental group (free on two generators). But are they homotopy equivalent?

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    Hint: $X$ and $Y$ have the same cohomology ring, the same homotopy groups, homotopy algebras, $K$-theory, etc, etc...2012-08-07

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Yes. Taking the wedge sum with a circle is the same as identifying two points (up to homotopy, with a nice space like the sphere which is homogeneous).

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    @QiaochuYuan: Fair enough. I was hoping there was some more general principle at work.2012-08-07
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This is actually a special case of the result that if $A \to X$ is a closed cofibration, and $f:A \to B$ is a map, then the natural map $M(f) \cup X \to B \cup_f X$ is a homotopy equivalence: here $M(f)$ is the mapping cylinder of $f$, and the result is 7.5.4 of my book Topology and Groupoids.

For your case, you have to take $A$ to consist of $4$ points, and $B$ to consist of $2$ points.

Here is part of the general picture

extract

and here is a picture of the special case you asked about but with just one pair of points identified:

sphere

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Is this right? EDIT: no. $X$ admits a surjection to $\mathbb{RP}^2$ which induces an inclusion on the $\mathbb{Z}/2$ valued cohomology rings. Therefore the cup product structure on $X$ is non-trivial and so $X$ cannot be homotopy equivalent to $Y$.

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    No, the map is trivial on $H^2$.2012-08-07