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Haryana Police Constable Model Paper 1
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© examsnet.com
Question : 41
Total: 100
If
3
x
2
+
kx
+
12
=
0
have two equal roots then value of k is:
+12
±10
±12
-12
Validate
Solution:
Given
,
The equation is
=
3
x
2
+
kx
+
12
=
0
Concept
:
If
b
2
−
4
ac
=
0
, we get two equal real roots.
Calculation
:
⇒
3
x
2
+
kx
+
12
=
0
Comparing in
a
x
2
+
b
x
+
c
=
0
⇒
a
=
3
,
b
=
k
and
c
=
12
If roots are equal, then
⇒
b
2
−
4
a
c
=
0
⇒
k
2
−
4
×
3
×
12
=
0
⇒
k
2
=
12
×
12
⇒
k
=
√
(
12
×
12
)
∴
k
=
±
12
© examsnet.com
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