1
JEE Main 2020 (Online) 8th January Morning Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
If the equation, x2 + bx + 45 = 0 (b $$ \in $$ R) has conjugate complex roots and they satisfy |z +1| = 2$$\sqrt {10} $$ , then :
A
b2 – b = 42
B
b2 + b = 12
C
b2 + b = 72
D
b2 – b = 30
2
JEE Main 2020 (Online) 8th January Morning Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
The mean and the standard deviation (s.d.) of 10 observations are 20 and 2 resepectively. Each of these 10 observations is multiplied by p and then reduced by q, where p $$ \ne $$ 0 and q $$ \ne $$ 0. If the new mean and new s.d. become half of their original values, then q is equal to
A
10
B
-20
C
-10
D
-5
3
JEE Main 2020 (Online) 8th January Morning Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
For a > 0, let the curves C1 : y2 = ax and C2 : x2 = ay intersect at origin O and a point P. Let the line x = b (0 < b < a) intersect the chord OP and the x-axis at points Q and R, respectively. If the line x = b bisects the area bounded by the curves, C1 and C2, and the area of
$$\Delta $$OQR = $${1 \over 2}$$, then 'a' satisfies the equation :
A
x6 – 12x3 + 4 = 0
B
x6 – 12x3 – 4 = 0
C
x6 + 6x3 – 4 = 0
D
x6 – 6x3 + 4 = 0
4
JEE Main 2020 (Online) 8th January Morning Slot
MCQ (Single Correct Answer)
+4
-1
Out of Syllabus
Change Language
Which one of the following is a tautology?
A
P $$ \wedge $$ (P $$ \vee $$ Q)
B
P $$ \vee $$ (P $$ \wedge $$ Q)
C
Q $$ \to $$ (P $$ \wedge $$ (P $$ \to $$ Q))
D
(P $$ \wedge $$ (P $$ \to $$ Q)) $$ \to $$ Q
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