Question

The nth term of an A.P. is given by Tn = 3 n -1 . Then the common difference of the A.P. is_______ *

1 point

For a given A.P. the first term is 5 and the 19th term is 95. Then ,the sum of its 19 terms is____ *

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Answer 1

Answer:

d = -3

S19 = 950

Step-by-step explanation:

Tn = 3n - 1

a or T1 = 3×3 - 1

a = 8

T2 = 3 ×2 - 1

= 5

common difference d = 5 - 8 = -3

first term, a = 5

T19 = 95

T19 = 5 + 18 d. = 95

d = 5 using Tn = a +( n-1)d

Sn = n/2{2a + (n - 1)d}

S19 = 19/2 ( 10 + 90d)

= 19 × (5 + 45)

= 19 × 50

S19 = 950

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