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Mathematics
If b1b2 = 2(c1 + c2) and b1, b2, c1, c2 are all real numbers, then at least one of the equations x2 + b1x + c1 = 0 and x2 + b2x + c2 = 0 has
Q. If
b
1
b
2
=
2
(
c
1
+
c
2
)
and
b
1
,
b
2
,
c
1
,
c
2
are all real numbers, then at least one of the equations
x
2
+
b
1
x
+
c
1
=
0
and
x
2
+
b
2
x
+
c
2
=
0
has
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A
real roots
85%
B
purely imaginary roots
8%
C
roots of the form
a
+
ib
(
a
,
b
∈
R
,
ab
=
0
)
4%
D
rational roots
3%
Solution:
We have equations
and Now,
x
2
+
b
1
x
+
c
1
=
0
D
1
=
b
1
2
−
4
c
1
and
x
2
+
b
2
x
+
c
2
=
0
D
2
=
b
2
2
−
4
c
2
Now,
D
1
+
D
2
=
b
1
2
+
b
2
2
−
4
(
c
1
+
c
2
)
=
b
1
2
+
b
2
2
−
2
b
1
b
2
[
∵
b
1
b
2
=
2
(
c
1
+
c
2
)
]
=
(
b
1
−
b
2
)
2
≥
0
⇒
At least one of
D
1
and
D
2
are non-negative real roots.