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Question
Mathematics
If |x2+x&x+1&x-2 2x2+3x-1&3x&3x-3 x2+2x+3&2x-1&2x-1|=ax-12, then 'a' is equal to :
Q. If
∣
∣
x
2
+
x
2
x
2
+
3
x
−
1
x
2
+
2
x
+
3
x
+
1
3
x
2
x
−
1
x
−
2
3
x
−
3
2
x
−
1
∣
∣
=
a
x
−
12
,
then 'a' is equal to :
7356
190
JEE Main
JEE Main 2015
Determinants
Report Error
A
12
21%
B
24
48%
C
- 12
18%
D
- 24
14%
Solution:
Δ
=
∣
∣
x
2
+
x
2
x
2
+
3
x
−
1
x
2
+
2
x
+
3
x
+
1
3
x
2
x
−
1
x
−
2
3
x
−
3
2
x
−
1
∣
∣
=
a
x
−
12
Operating
R
2
→
R
2
−
(
R
1
+
R
3
)
gives,
Δ
=
∣
∣
x
2
+
x
−
4
x
2
+
2
x
+
3
x
+
1
0
2
x
−
1
x
−
2
0
2
x
−
1
∣
∣
⇒
Δ
=
−
(
−
4
)
∣
∣
x
+
1
2
x
−
1
x
−
2
2
x
−
1
∣
∣
=
4
(
2
x
−
1
)
∣
∣
x
+
1
1
x
−
2
1
∣
∣
=
4
(
2
x
−
1
)
(
x
+
1
−
x
+
2
)
=
4
(
2
x
−
1
)
(
3
)
=
24
x
−
12
=
a
x
−
12
(given)
⇒
a
=
24