Question

Which term of the A.P 21, 18, 15,,,,,,,,,,,,,,,, is -81

Answer 1

Answer:

The 35 th term of AP is -81

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Step-by-step explanation:

Here,

a= 2 1

 Common difference ( d) = 18 - 21 = - 3

n th term ( t n) = -81

We know,

t n = a + (n -1 )d

or, -81 = 21 + ( n - 1) * ( -3 )

or. -102 = - 3 n + 3

or, -105 = - 3n

or, n = 105 /3 = 35