Question

find sum of first 51 term of an ap whose second and third termare 14 and 18 respectively​

Answer 1

Answer:

Hey mate here is ur ans

Sum of first 51 terms = 561

Step-by-step explanation:

Given

2nd term = 14

a+d =14 ......(1)

3rd term = 18

a + 2d= 18.....(2)

subtract (1) from (2) we get

d = 4

put this value in (1)

a + 4= 14

a = 10

Now, sum of first 51 terms

$= \frac{n}{2} (2a + (n - 1)d) \\ = \frac{51}{2} (2(10) + (51 - 1)4) \\ = \frac{51}{2} (20 + 50(4)) \\ = \frac{51}{2} (20 + 200) \\ = \frac{51}{2} (220) \\ = 51(110) \\ = 561$

Hope this helps u

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Answer 2

Refers to attachment ♡~