Question

How many terms of the arithmetic sequence 3,5,7,...... must be added to get 255 ?

Answer 1

Answer:

sn= 255

a=3

d= a2-a1= 5-3= 2

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

255= n/2(3+(n-1)2)

255= n/2(3+2n-2)

255=n/2(2n+1)

255×2=2n²+n

510=2n²+n

next solve this equation