a5= a + (n -1) d2 = -14 + 4d16 = 4dd = 4Sn = [2a + (n – 1) d]40 = [2(-14) + (n -1) (4)]40 = 12n2 – 16n2n2 – 16n -40 = 0n2 – 8n -20 = 0n2 – 10n + 2n – 20 = 0(n – 10) (n + 2) = 0n = 10 and n = -2 (not possible)

1 2 3 4 5 A 5 B 5 C 5 D 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66

RD Sharma - Mathematics

Exercise 9.1

1 2 3

Exercise 9.2

1 2 3 4 5 6 7 8 9 10 11 12

Exercise 9.3

1 2 A 2 B 2 C 2 D 2 E 3 A 3 B 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47

Exercise 9.4

1 2 3 4 5 6 7 8

Exercise 9.5

CCE - Formative Assessment

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42

Q. 5 B

How many terms ar

Class 10th RD Sharma - Mathematics 9. Arithmetic Progressions

Answer :

a₅= a + (n -1) d

2 = -14 + 4d

16 = 4d

d = 4

S_n = [2a + (n – 1) d]

40 = [2(-14) + (n -1) (4)]

40 = 12n² – 16n

2n² – 16n -40 = 0

n² – 8n -20 = 0

n² – 10n + 2n – 20 = 0

(n – 10) (n + 2) = 0

n = 10 and n = -2 (not possible)

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