How many terms of the sequence 18,16,14 - - - - should be taken so that there sum is zero
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Heya !!!
AP = 18 , 16 , 14 .....
Here,
First term ( A ) = 18
Common Difference ( D ) = 16-18 = -2
Sn = 0
N/2 × [ 2A + ( N - 1 ) × D ] = 0
N/2 × [ 2 × 18 + ( N - 1 ) × -2 ] = 0
N/2 × ( 36 - 2N + 2 ) = 0
N/2 × 38 - 2N = 0
N/2 × 2 ( 19 - N ) = 0
-N² + 19N = 0
N ( - n + 19 ) = 0
- n + 19 = 0
- n = -19
n = 19
Hence,
19 terms should be taken to get their sum as 0.
★ HOPE IT WILL HELP YOU ★
AP = 18 , 16 , 14 .....
Here,
First term ( A ) = 18
Common Difference ( D ) = 16-18 = -2
Sn = 0
N/2 × [ 2A + ( N - 1 ) × D ] = 0
N/2 × [ 2 × 18 + ( N - 1 ) × -2 ] = 0
N/2 × ( 36 - 2N + 2 ) = 0
N/2 × 38 - 2N = 0
N/2 × 2 ( 19 - N ) = 0
-N² + 19N = 0
N ( - n + 19 ) = 0
- n + 19 = 0
- n = -19
n = 19
Hence,
19 terms should be taken to get their sum as 0.
★ HOPE IT WILL HELP YOU ★
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