Find the sum of 2+4+6+8...+70. State if it's geometric or arithmetic?

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Answer 1 · 2018-04-20T18:06:34

This is an Arithmetic sequence.

Sum #=1260#

Here #d= 2# is the Common difference.

#a=2# is the First term.

#l=70# is the last term.

We know that #n_(th)# term of this sequence is given by #a_n# :-

#a_n =a+(n-1)d#

#rArr 70=2+(n-1)2#

#rArr 34=n-1#

#rArr n=35=#Total number of terms in the given arithmetic sequence.

#sum a_n = (n(a+l))/2#

#:.# Sum #=(35(2+70))/2=1260#