Question

AP.7. 13. 19,..........205​

Answer 1

Step-by-step explanation:

205 = n/2 { 14 +{n-1} ×6}

410 = n{ 8+6n}

210= n { 4 +3n}

3n^2 + 4n -210 =0

Answer 2

Answer:

a=t1=7

d=6

tn=205

n=2

Sn=?

tn=a+(n-1)d

205=7+(n-1)6

205-7=(n-6)

198=(n-1)6

198/6=n-1

33=n-1

n=33+1

n=34

Sn=n/2×{t1+tn}

=34/2×{7+205}

=17×212

=3604

Step-by-step explanation:

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