Question

Find the sum of 'n' terms in following series

ii) 42+62 +82 + .........​

Answer 1

Answer:

hey mate!

Step-by-step explanation:

Sn=n/2(2a+(n-1)d);d=20,a=42!

 =>n/2(84+(n-1)20)

   =>solving this!

  =>Sn=62n-20!

ans.!

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Answer 2

given that

a= 42

a2 =62

d=a2 -a

= 62 - 42

= 20

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

n/2[2 ×42 + (n-1) × 20]

n/2 [ 84 + 20n-20 ]

n/2 [64 + 20n ]

s ^n = n/2 [64 +20n]