∑n = 1∞2n2 + n + 1n! is equal to
2e - 1
2e + 1
6e - 1
6e + 1
If a < 1, b = ∑k = 1∞akk, then a is equal to
∑k = 1∞- 1kbkk
∑k = 1∞- 1k - 1bkk!
∑k = 1∞- 1kbkk - 1!
∑k = 1∞- 1k - 1bkk + 1!
1 + 24 + 24 58 + 24 58 812 + 24 58 812 1116 + . . . . is equal to:
4 - 23
163
43
432
If x < 1 and y = x - x22 + x33 - x44 + . . . , then x is equal to
y + y22 + y33 + . . .
y - y22 + y33 - y44 + . . .
y + y22! + y33! + . . .
y - y22! + y33! - y44! + . . .
If Sn = 13 + 23 + ... + n3 and Tn = 1 + 2 + ... + n, then
Sn = Tn3
Sn = Tn2
For any integer n ≥ 1, the sum ∑k = 1nkk + 2 is equal to
nn + 1n + 26
nn + 12n + 16
nn + 12n + 76
nn + 12n + 96
If 1 + x + x2 + x35 = ∑k = 015akxk, then ∑a2k = 07k = 0
128
256
512
1024
If α = 52 ! 3 + 5 . 73 ! 32 + 5 . 7. 94! 33 + . . . , thenα2 + 4α is equal to
21
23
25
27
B.
Given that, α = 52 ! 3 + 5 . 73 ! 32 +5 . 7 . 94 ! 33 + . . . . . .iWe know that,1 + xn = 1 + nx1! + nn - 12!x2 + nn - 1n - 23!x3 + . . . . . .ii On compairing eqs. i and ii, with respect to factorialnn - 1x2 = 53 . . . iiinn - 1n - 2x3 = 5 . 732 . . . ivandnn - 1n - 2n - 3x4 = 5 . 7 . 933 . . . vOn dividing eq. iv by iii and eq. v by iv, we getn - 2x = 73 . . . viand n - 3x = 3 . . . viiAgain, dividing eq. vi by vii, we getn - 2 n - 3 = 79
⇒9n - 18 = 7n - 21⇒2n = - 3⇒ n = - 32On putting the value of n in eq vi, we get- 32 - 2x = 73 ⇒ x = - 23∴From eq. ii1 - 23- 32 = 1 + 1 + 52 ! 3 + 5 . 73 ! 32 + . . .⇒ 332 - 2 = 52 ! 3 + 5 . 73 ! 32 + . . . ⇒ α = 332 - 2 from eq. iNow, α2 + 4α = 332 - 22 + 4332 - 2 = 27 + 4 - 4 332 + 4 . 332 - 8 = 23
11 . 3 + 12 . 5 + 13 . 7 +14 . 9 + . . . = ?
2loge2 - 2
2 - loge2
2loge4
loge4
If l, m, n are in arithmetic progression, then the straight line b + my + n = 0 will pass through the point
(- 1, 2)
(1, - 2)
(1, 2)
(2, 1)