Find the sum of 34+32+30.....+10 by using ap formula
Answers
Answer: 286
Step-by-step explanation:
here we have ; a = 34 ,
d = a2 - a1
= 32 - 34
d = - 2
nth term = 10
by formula of nth term i.e, nth term = a + (n - 1) d
substituting all values we get , 10 = 34 + (n - 1) - 2
10 = 34 + -2n + 2
10 - 34 -2 = - 2n
10 - 36 = -2n
- 26 = -2n
n = -26 / -2
n = 13
now by formula to find sum of an A.P i.e, sum of n terms = n/2 [a + nth term]
substituting all values we get , sum of n terms = 13/2[34 + 10]
sum of n terms = 13/2(44)
sum of n terms = 13 *22
by solving we will get sum of n terms = 286 which is our required answer
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