Question

sum of first n terms of an ap whose first term is 8 and the common difference is 20 is equal to the sum of first 20 terms of an ap whose first term is minus 30 and common difference is 8 find n ​

Answer 1

Step-by-step explanation:

Considering the two sums as An and Sn'

Now Sn =Sn'

n/2(2a+(n-1)d) = n/2(2a'+(n-1)d')

n/2(16+(n-1)20). = 20/2(-60+19*8)

n/2(16+20n -20) = 10*92

16n + 20n^2 -20n = 10*92*2

20n^2 -4n = 1840

by factorisation methods and finding roots of the quadratic equation

n= 10

Note: always take integer and positive number for the value of n

hope this helps you

please mark as brainest

I will be thankful to you