Question

a=2,d=8,Sn=210,find n and an
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Answer 1

Answer:

105+1 =106

Step-by-step explanation:

hope it helps you

Answer 2

Answer:

Take Sn=240,210 is not possible n=8,An=58

Step-by-step explanation:

a=2,d=8,Sn=240

Sn= n/2( 2*2+(n-1)*8)

240=n/2(4+8n-8)

240*2=n(8n-4)

480=4n(2n-1)

120=2n²-n

2n²-n-120=0

2n²-16n+15n-120=0

2n( n-8)+15(n-8)=0

(n-8)(2n+15)=0

n=8 cm,-7.5 cm

So An=a+(n-1)d

=2+7*8

=2+56=58