Sum of first n terms of an AP is an(n-1).The sum of squares of these terms is ?

Dear student

We have,Sn=ann-1Sn-1=an-1n-2Now, an=Sn-Sn-1an=ann-1-an-1n-2an=an-1n-n+2an=2an-1Now, a1=2a1-1=0a2=2a2-1=2aa3=2a3-1=4aa4=2a4-1=6aa5=2a5-1=8aand so on.Now, sum of the squares of the terms is given by:S=a12+a22+a32+a42+a52+...+an2=0+4a2+16a2+36a2+64a2+....+4a2n-12=4a21+4+9+16+....+n-12=4a21+22+32+42+....+n-12=4a2×nn-12n-16=23a2nn-12n-1
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n mean newton
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