Question

Example 15. Sum of how many terms of
A.P. 54, 51, 48, ... will be 513? vedio me samgao​

Answer 1

Step-by-step explanation:

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Answer 2

Answer:

here 1st term a=54,common difference b=51-54= -3

let sum of n terms will be 513

513=n/2{2.54+(n-1)(-3)}

513=n/2(108+3-3n)

1026=n(111-3n)

1026=3n(37-n)

342=37n-n^2

n^2-37n+342=0

n^2--19n-18n+342=0

n(n-19)-18(n-19)=0

(n-18)(n-19)=0

n-18=0

n=18

n-19=0

n=19

sum of 18 terms will be 513

sum of 19 terms will be 513

here value of one term is zero