513=n%2(108+(n-1)-3)

1.	513=n%2(108+(n-1)-3)
Answer» Ise solve kero answer aa jayega Yes i will tell you ,513=n/2(2×54+(n-1)-3) N = 18,19 Can any one tell why two values of terms are coming? 54, 51, 48,...........First term a = 54Common difference d = 51 - 54 = -3Let n is the number of terms.Given, sum = 513=> (n/2){2a + (n - 1)d} = 513=> n{2a + (n - 1)d} = 5132=> n{254 + (n - 1)(-3)} = 1026=> n{108 - 3n + 3} = 1026=> n{111 - 3n} = 1026=> 111n - 3n2\xa0= 1026=> 3n2\xa0- 111n + 1026 = 0=> n2\xa0- 37n + 342 = 0 {divide by 3}=> (n - 18)*(n - 19) = 0=> n = 18, 19Hence, number of terms is either 18 or 19

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