1
WB JEE 2023
MCQ (Single Correct Answer)
+1
-0.25
Change Language

The average length of all vertical chords of the hyperbola $${{{x^2}} \over {{a^2}}} - {{{y^2}} \over {{b^2}}} = 1,a \le x \le 2a$$, is :

A
$$b\{ 2\sqrt 3 - \ln (2 + \sqrt 3 )\} $$
B
$$b\{ 3\sqrt 2 + \ln (3 + \sqrt 2 )\} $$
C
$$a\{ 2\sqrt 5 - \ln (2 + \sqrt 5 )\} $$
D
$$a\{ 5\sqrt 2 + \ln (5 + \sqrt 2 )\} $$
2
WB JEE 2023
MCQ (Single Correct Answer)
+1
-0.25
Change Language

The value of 'a' for which the scalar triple product formed by the vectors $$\overrightarrow \alpha = \widehat i + a\widehat j + \widehat k,\overrightarrow \beta = \widehat j + a\widehat k$$ and $$\overrightarrow \gamma = a\widehat i + \widehat k$$ is maximum, is

A
3
B
$$-$$3
C
$$ - {1 \over {\sqrt 3 }}$$
D
$${1 \over {\sqrt 3 }}$$
3
WB JEE 2023
MCQ (Single Correct Answer)
+1
-0.25
Change Language

If the vertices of a square are $${z_1},{z_2},{z_3}$$ and $${z_4}$$ taken in the anti-clockwise order, then $${z_3} = $$

A
$$ - i{z_1} - (1 + i){z_2}$$
B
$${z_1} - (1 + i){z_2}$$
C
$${z_1} + (1 + i){z_2}$$
D
$$ - i{z_1} + (1 + i){z_2}$$
4
WB JEE 2023
MCQ (Single Correct Answer)
+1
-0.25
Change Language

If the n terms $${a_1},{a_2},\,......,\,{a_n}$$ are in A.P. with increment r, then the difference between the mean of their squares & the square of their mean is

A
$${{{r^2}\{ {{(n - 1)}^2} - 1\} } \over {12}}$$
B
$${{{r^2}} \over {12}}$$
C
$${{{r^2}({n^2} - 1)} \over {12}}$$
D
$${{{n^2} - 1} \over {12}}$$
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