Question

# The sum up to n terms of an AP in which the first term is a, last term is l, and the common difference is d, is ___n2(2a+(n−1)d)  n2(a+l)  n2(a+(n−1)d)  n2(2a+l)

Solution

## The correct options are A n2(2a+(n−1)d)   B n2(a+l)  We know that sum upto n terms of an AP with first term a and common difference d is n2(2a+(n−1)d) =n2(a+a+(n−1)d)----- (1) We know that a+(n−1)d is the  nth term, which is the last term. Substituting the value of last term i.e. a+(n−1)d equals to l in formulae (1). Hence, Sn=n2(a+l)

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