Question

please answer these two questions I will be thankful to you and I will follow you and I will mark it as brainliest

but it's my warning jise nahi aata vo answer na de otherwise I will report it​​

Answer 1

Answer:

n = 11

Step-by-step explanation:

first AP:

a1 = 8

d = 20

Sn = $\frac{n}{2}$ (2a+(n-1)d)

∴ Sn = $\frac{n}{2}$ ( 2 x 8 + ( n - 1) 20)

Sn =  $\frac{n}{2}$ ( 16 + 20n - 20)

Sn =  $\frac{n}{2}$ (  20n - 4 )

Sn =  $\frac{n}{2}$ x 2 ( 10n - 2)  [we took common factor here so that we can cut it with 2]

Sn = n (10 n - 2)

second AP:

a = -30

d = 8

S2n = $\frac{2n}{2}$ ( 2 x -30 + ( 2n - 1) 8 )

S2n = n (-60 + 16n - 8 )

S2n = n (-68 + 16n )

They have given that the sum of first n terms of first AP = sum of 2n terms of second AP

∴ n (10 n - 2) = n (-68 + 16n )              

[we cancel 'n' bcz it becomse divison when bought to the other side]

(10 n - 2) = (-68 + 16n )  

10 n - 2 = -68 + 16n  

-2 + 68 = 16n - 10n

66 = 6n

n = $\frac{66}{6}$ = 11

hope it helped! please mark as brainliest