Find the sum of first n terms.(a) \(\frac{n(n+1)}{2}\)(b) \((\frac{n(n+1)}{2})^3\)(c) \(\frac{n(n+1)(2n+1)}{6}\)(d) \((\frac{n(n+1)}{2})^2\)The question was asked during an online interview.My doubt is from Sum to n Terms of Special Series topic in portion Sequences and Series of Mathematics – Class 11

Find the sum of first n terms.(a) \(\frac{n(n+1)}{2}\)(b) \((\frac{n(n

1.	Find the sum of first n terms.(a) \(\frac{n(n+1)}{2}\)(b) \((\frac{n(n+1)}{2})^3\)(c) \(\frac{n(n+1)(2n+1)}{6}\)(d) \((\frac{n(n+1)}{2})^2\)The question was asked during an online interview.My doubt is from Sum to n Terms of Special Series topic in portion Sequences and Series of Mathematics – Class 11
Answer» CORRECT choice is (a) \(\FRAC{N(n+1)}{2}\) The explanation is: SUM of FIRST n terms = 1+2+3+4+……+n => (n/2) (a + an) = (n/2) (1+n) = \(\frac{n(n+1)}{2}\).

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