Find the number of terms of AP 54,51,48..............so that their sum

1.	Find the number of terms of AP 54,51,48..............so that their sum is 513
Answer» a=54; d=-3; n=?; Sn=513 Sn=n÷2{2a+(n-1)d}513 =n÷2{2(54)+(n-1)(-3)}513×2=n{108-3n+3} 1026=n{111-3n}1026=111n-3n^23n^2-111n+1026=0Divide by 3n^2-37n+342=0n^2-19n-18n+342=0n(n-19)-18(n-19)=0(n-18)(n-19)=0therefore;n=18or19 Answer bhai sn wale formula par rakhoaajayega.pakka No. Of n term is 19..

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