if the sum of 7 terms of an ap is 49 and that of first 17 term is 289. Find the sum of n terms
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7/2(2a+6d)=49
a+3d=7
s=17/2(2a+16d)
289=17(a+8d)
17=a+8d
on solving these equations,5d=10
d=2 and a=1
therefore sum of n terms=n/2(2a+(n-1)d)
=n/2(2*1+(n-1)2)
=n/2*2(1+n-1)
=n*n=n²
a+3d=7
s=17/2(2a+16d)
289=17(a+8d)
17=a+8d
on solving these equations,5d=10
d=2 and a=1
therefore sum of n terms=n/2(2a+(n-1)d)
=n/2(2*1+(n-1)2)
=n/2*2(1+n-1)
=n*n=n²
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