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Byju's Answer
Standard VII
Mathematics
Powers and Exponents
If a →=2 i--7...
Question
If
a
→
=
2
i
^
-
7
j
^
+
k
^
,
b
→
=
i
^
+
3
j
^
-
5
k
^
and
a
→
.
m
b
→
=
120
,
then
m
=
_
_
_
_
_
_
_
_
_
_
_
_
_
.
Open in App
Solution
Given:
a
→
=
2
i
^
-
7
j
^
+
k
^
b
→
=
i
^
+
3
j
^
-
5
k
^
a
→
·
m
b
→
=
120
a
→
·
m
b
→
=
120
⇒
m
a
→
·
b
→
=
120
⇒
m
2
1
+
-
7
3
+
1
-
5
=
120
⇒
m
2
-
21
-
5
=
120
⇒
m
-
24
=
120
⇒
m
=
-
120
24
⇒
m
=
-
10
2
⇒
m
=
-
5
Hence,
m
=
-
5
.
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0
Similar questions
Q.
Let the distance between vectors are given as follows :
(
i
)
4
i
+
3
j
−
6
k
,
−
2
i
+
j
−
k
be
√
k
(
i
i
)
−
2
i
+
3
j
+
5
k
,
7
i
−
k
be
m
√
n
Find
k
−
(
m
∗
n
)
?
Q.
If
A
B
=
−
i
−
2
j
−
6
k
,
B
C
=
2
i
−
j
+
k
,
A
C
=
i
−
3
j
−
5
k
. then
∠
B
=
Q.
Prove that the following vectors are coplanar:
(i)
2
i
^
-
j
^
+
k
^
,
i
^
-
3
j
^
-
5
k
^
and
3
i
^
-
4
j
^
-
4
k
^
(ii)
i
^
+
j
^
+
k
^
,
2
i
^
+
3
j
^
-
k
^
and
-
i
^
-
2
j
^
+
2
k
^
Q.
The projection of
a
=
3
i
−
j
+
5
k
on
b
=
2
i
+
3
j
+
k
is
Q.
If
a
→
=
2
i
^
-
3
j
^
+
5
k
^
,
b
→
=
3
i
^
-
4
j
^
+
5
k
^
and
c
→
=
5
i
^
-
3
j
^
-
2
k
^
,
then the volume of the parallelopiped with conterminous edges
a
→
+
b
,
→
b
→
+
c
,
→
c
→
+
a
→
is
(a) 2
(b) 1
(c) −1
(d) 0
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