Question

find the sum of first 15th term an AP 5 8 11 14​

Answer 1

Answer:

a = 5

d = 8-5 = 3

S15 = 15/2 [2×5 + 14(3)]

= 15/2 [10+42]

= 15/2 [52]

= 15×26

= 390

Answer 2

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To Solve:

• find the sum of first 15th term an AP 5 8 11 14

Given:

• AP - 5 8 11 14

Solⁿ:

AP- 5 8 11 14

a¹ = 5

d = a² - a¹ = 8 - 5 = 3

d = 3

n = 15

Sⁿ = ?

Formula:

$Sⁿ = \frac{n}{2} (2a + (n - 1)d) \\ \\ Sⁿ = \frac{15}{2} (2(5) + (15 - 1)3) \\ \\ Sⁿ = \frac{15}{2} (10 + 42) \\ \\ Sⁿ = \frac{15}{2} (52) \\ \\ Sⁿ = \frac{15}{2} \times 52 \\ \\ { \boxed{Sⁿ = 390}}$

HOPE IT HELPS :)