Question

an=4 Sn=14 d=2find n and a




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Answer 1

Answer:

Sn=14,d=2

sn=n/2(2f+(n-1)d)

14=n/2(2f+2n-2)

28=n(2f+2n-2)

28/n=2f+2n-2

28/n+2/1=2f+2n

28+2n/2=14+n

14+n=2f+2n

14=2f+2n-n

14=2f+n

14/2=f+n

7=f+n

n=4 & a=3

checking..sn=n/2(a+an)

= 4/2(3+4)

=2×7=14