Question

find the sum of the first 20 terms of an A.P whose common different is 3 times of its first term and its 5th term is 26​

Answer 1

Answer:

Step-by-step explanation:

t5=a+4d=26

d=3a

a+4*3a   =26

13a  = 26

a=2

d=6

sum of 20 terms = 20/2 *(2*2+[20-1]6)

sum of 20 terms = 1180

Answer 2

Step-by-step explanation:

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