Question

Find the 18th term from last term of the AP-3,-10,-17,...........,-276.

Answer 1

10 , 7 , 4 , ...... , ( -62 ) are in A.P

first term = a = 10

common difference = d = a3 - a2 = 4 - 7 = -3

last term = n th term = an = l = - 62

we know that ,

a + ( n - 1 ) d = l

put above values in the formula,

10 + ( n - 1 ) ( - 3 ) = -62

⇒ ( n- 1 ) ( -3 ) = -62 - 10

⇒ ( n - 1 ) ( - 3 ) = - 72

⇒ ( n - 1) = ( - 72 ) / ( - 3 )

⇒ n - 1 = 24

∴ n= 24 +1

n = 25

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Answer 2

The numbers are -3,-10,-17,-24,-31,-38,-45,-52,-59,-66,-73,-80,-87,-94,-101,-108,-115,-122,-129,-136,-143

Therefore, the 18th term is -143.

As, every number graph is 7...