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Hatcher-Algebraic-Topology
· Problem 3F.3
Cohomology
Mathematics — Graph Theory · limits-and-ext
Problem
Show that
E
x
t
(
A
,
Q
)
=
0
\mathrm{Ext}(A, \mathbb{Q}) = 0
Ext
(
A
,
Q
)
=
0
for all
A
A
A
. [Consider the homology with
Q
\mathbb{Q}
Q
coefficients of a Moore space
M
(
A
,
n
)
M(A, n)
M
(
A
,
n
)
.]
Related theory
Infinite Limits And Limits At Infinity
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