Math, asked by anishchandaliya, 9 months ago

if second and third terms of an a.p are 3 ,5 respectively then the sum of first 20 term

Answers

Answered by IshikaThakur29
5

Answer:

second term (a+d)=3

third term(a+2d)=5

by elimination

a+d =3

a+2d=5

d=2 , a=1

1,3,5,..........

Sn= n/2[2a+(n-1)d]

S20=20/2[2×1+(20-1)2]

S20=10[2+(19)×2]

S20=10[2+38]

S20=10(40)

S20=400

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