Question

the sum of n term of an ap is 5n square - 4n find the first five term of the AP describe this question solution




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Answer 1

Answer:

1,12,23,34,45,56,... is the AP for the given problem

Answer 2

Answer:

given Sₙ = 5n² - 4n

then Sₙ₋₁ = 5(n-1)² - 4(n - 1)

=> 5 ( n² - 2n + 1) - 4(n - 1)

=5n² - 10n + 5 - 4n + 4

=> 5n² - 14n + 9

Formula used, nth term aₙ= Sn - Sₙ₋₁

=> aₙ = 5n² - 4n - ( 5n² - 14n + 9)

=> 5n² - 4n - 5n² +14n - 9

=> aₙ = 10n - 9

put n = 1, 2, 3, 4 and 5 in the above equation to get first 5 terms of A.P.

therefore first five terms are

1, 11, 21, 31, 41