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Assignment-1 Binomial Theorem 1685019641490

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MATHEMATICS : VIKAS GUPTA

ASSIGNMENT-1
11 11
 2 1   1 
1. Find the coefficients : (i) x7 in  a x   (ii) x7 in  ax  2 
 bx   bx 

(iii) Find the relation between a & b , so that these coefficients are equal.

2. If the coefficients of (2r + 4)th , (r  2)th terms in the expansion of (1 + x)18 are equal , find r.

3. If the coefficients of the rth, (r + 1)th & (r + 2)th terms in the expansion of (1 + x)14 are in AP, find r.

10 8
 x 3   1 1/3 1/5 
4. Find the term independent of x in the expansion of (a)   2 (b)  x  x
 3 2 x  
2 

5. If the coefficients of 2nd, 3rd & 4th terms in the expansion of (1 + x)2n are in AP, show that 2n²  9n + 7 = 0.

6. If a, b, c & d are the coefficients of any four consecutive terms in the expansion of (1 + x)n, n  N, prove

VIBRANT ACADEMY
a c 2b
that a  b  c  d  b  c .

11
 7
7. In the expansion of  1  x   find the term not containing x.
 x

8. Show that coefficient of x5 in the expansion of (1 + x²)5 . (1 + x)4 is 60.

9.
unacademy  2
Prove that the ratio of the coefficient of x10 in (1  x²)10 & the term independent of x in  x  
 x
10

is 1 : 32 .

n 4
10. Let (1+x²)² . (1+x)n = a K . xK . If a1 , a2 & a3 are in AP, find n.
K0

8
 2 log 4x  44 1 
Find the value of x for which the fourth term in the expansion,  5
5 5
11.   is 336.
3 2 x 1  7 
 5log5 

12. Find the coefficient of xr in the expression of :


(x + 3)n1 + (x + 3)n2 (x + 2) + (x + 3)n3 (x + 2)2 + ..... + (x + 2)n1

n
r  1 3r 7r 15r 
13. Find the sum of the series  (1) . nC r    3r  4 r  .....up to m terms 
r 2r
r0  2 2 2 2 

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ANSWERS

11C
a6 11
1C
a5 5
1. (i) (ii) (iii) ab = 1 2. r = 6 3. r = 5 or 9 4. (a) (b) T6 = 7
5
b5 6
b6 12

5
7. 1+  11
1C
2k . 2kC
k 7k 10. n = 2 or 3 or 4 11. x = 0 or 1 12. nC (3nr 
r 2nr)
k1

2 mn
1
13.
 2  1  2 
n mn

VIBRANT ACADEMY

unacademy

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