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Mathematics
Mathematics
Problem
If
(
a
+
3
b
)
⋅
(
7
a
−
5
b
)
=
0
(a + 3b) \cdot (7a - 5b) = 0
(
a
+
3
b
)
⋅
(
7
a
−
5
b
)
=
0
and
(
a
−
4
b
)
⋅
(
7
a
−
2
b
)
=
0
(a - 4b) \cdot (7a - 2b) = 0
(
a
−
4
b
)
⋅
(
7
a
−
2
b
)
=
0
. Then, the angle between
a
a
a
and
b
b
b
is a.
60
∘
60^\circ
6
0
∘
b.
30
∘
30^\circ
3
0
∘
c.
90
∘
90^\circ
9
0
∘
d. None of these
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