answer both the questions... It is of 11th standard maths
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11. a=3
d=7-3=4
an=a+(n-1)d
=3+(n-1)4
=3+4n-4
an=4n-1-----(1)
sum of n terms Sn= n/2(a+an)
=n/2(3+4n-1)
=n/2(2+4n)
=n/2*2+4n
=4n2
sn=4n2
d=7-3=4
an=a+(n-1)d
=3+(n-1)4
=3+4n-4
an=4n-1-----(1)
sum of n terms Sn= n/2(a+an)
=n/2(3+4n-1)
=n/2(2+4n)
=n/2*2+4n
=4n2
sn=4n2
pragx:
I don't think it's a question of arithmetic progression because D is not same
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