1
WB JEE 2019
MCQ (Single Correct Answer)
+1
-0.25
Change Language
If $$A = \left( {\matrix{ 5 & {5x} & x \cr 0 & x & {5x} \cr 0 & 0 & 5 \cr } } \right)$$ and $$|A{|^2} = 25$$, then | x | is equal to
A
$${1 \over 5}$$
B
5
C
52
D
1
2
WB JEE 2019
MCQ (Single Correct Answer)
+1
-0.25
Change Language
Let A and B be two square matrices of order 3 and AB = O3, where O3 denotes the null matrix of order 3. Then,
A
must be A = O3 , B = O3
B
if A $$ \ne $$ O3, must be B $$ \ne $$ O3
C
if A = O3, must be B $$ \ne $$ O3
D
may be A $$ \ne $$ O3, B $$ \ne $$ O3
3
WB JEE 2019
MCQ (Single Correct Answer)
+2
-0.5
Change Language
The system of equations

$$\eqalign{ & \lambda x + y + 3z = 0 \cr & 2x + \mu y - z = 0 \cr & 5x + 7y + z = 0 \cr} $$

has infinitely many solutions in R. Then,
A
$$\lambda $$ = 2, $$\mu $$ = 3
B
$$\lambda $$ = 1, $$\mu $$ = 2
C
$$\lambda $$ = 1, $$\mu $$ = 3
D
$$\lambda $$ = 3, $$\mu $$ = 1
4
WB JEE 2018
MCQ (Single Correct Answer)
+1
-0.25
Change Language
If $$\left| {\matrix{ { - 1} & 7 & 0 \cr 2 & 1 & { - 3} \cr 3 & 4 & 1 \cr } } \right| = A$$, then $$\left| {\matrix{ {13} & { - 11} & 5 \cr { - 7} & { - 1} & {25} \cr { - 21} & { - 3} & { - 15} \cr } } \right|$$ is
A
$${A^2}$$
B
$${A^2} - A + {I_3}$$
C
$${A^2} - 3A + {I_3}$$
D
$$3{A^2} + 5A - 4{I_3}$$
WB JEE Subjects
EXAM MAP
Medical
NEET
Graduate Aptitude Test in Engineering
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CBSE
Class 12