Question

How many terms are there in the AP 21, 18, 15, . . . – 81 ?​

Answer 1

Answer:

There are 35 terms

Step-by-step explanation:

a = t1 = 21

t2 = 18 , t3 = 15 , .....

tn = -81

d = t2 - t1 = 18 - 21 = -3

The nth term of an AP,

tn = a + ( n-1 ) d

-81 = 21 + ( n-1 ) (-3)

-81 = 21 + ( -3n + 3 )

-81 = 21 - 3n + 3

-81 = 24 - 3n

-81 -24 = -3n

-105 = -3n

-35 = -n

n = 35

Answer 2

Answer:

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Step-by-step explanation:

hope it helps u