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Mathematics
Problem
If
log
3
(
x
)
=
p
\log_3(x) = p
lo
g
3
(
x
)
=
p
and
log
7
(
x
)
=
q
\log_7(x) = q
lo
g
7
(
x
)
=
q
, which of the following yields
log
21
(
x
)
\log_{21}(x)
lo
g
21
(
x
)
? (a)
p
q
pq
pq
(b)
1
p
+
q
\frac{1}{p+q}
p
+
q
1
(c)
1
p
−
1
+
q
−
1
\frac{1}{p^{-1}+q^{-1}}
p
−
1
+
q
−
1
1
(d)
p
q
p
−
1
+
q
−
1
\frac{pq}{p^{-1}+q^{-1}}
p
−
1
+
q
−
1
pq
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