1
JEE Main 2018 (Online) 16th April Morning Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
Let A = $$\left[ {\matrix{ 1 & 0 & 0 \cr 1 & 1 & 0 \cr 1 & 1 & 1 \cr } } \right]$$ and B = A20. Then the sum of the elements of the first column of B is :
A
210
B
211
C
231
D
251
2
JEE Main 2018 (Online) 16th April Morning Slot
MCQ (Single Correct Answer)
+4
-1
Out of Syllabus
Change Language
The coefficient of x2 in the expansion of the product
(2$$-$$x2) .((1 + 2x + 3x2)6 + (1 $$-$$ 4x2)6) is :
A
107
B
106
C
108
D
155
3
JEE Main 2018 (Online) 16th April Morning Slot
MCQ (Single Correct Answer)
+4
-1
Out of Syllabus
Change Language
The sum of the first 20 terms of the series

$$1 + {3 \over 2} + {7 \over 4} + {{15} \over 8} + {{31} \over {16}} + ...,$$ is :
A
$$38 + {1 \over {{2^{19}}}}$$
B
$$38 + {1 \over {{2^{20}}}}$$
C
$$39 + {1 \over {{2^{20}}}}$$
D
$$39 + {1 \over {{2^{19}}}}$$
4
JEE Main 2018 (Online) 16th April Morning Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
Let $${1 \over {{x_1}}},{1 \over {{x_2}}},...,{1 \over {{x_n}}}\,\,$$ (xi $$ \ne $$ 0 for i = 1, 2, ..., n) be in A.P. such that x1=4 and x21 = 20. If n is the least positive integer for which $${x_n} > 50,$$ then $$\sum\limits_{i = 1}^n {\left( {{1 \over {{x_i}}}} \right)} $$ is equal to :
A
$${1 \over 8}$$
B
3
C
$${{13} \over 8}$$
D
$${{13} \over 4}$$
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