Question

16added to the sum of first few terms of the arithmetic sequence 9,11,13,.....gave 256. how many terms were added?

Answer 1

Answer:

sum of an ap = n/2(2a + (n-1)d)

256 = n/2(2*9 + (n-1)2) + 16

240 = n/2 (18 + 12n-12)

240 = n/2(6 + 12n)

240 * 2/n = 6 + 12n

480/n = 6 + 12n

480 = 6n + 12n^2

12n^2 + 6n - 480 = 0   (/6)

2n^2 + n - 80 = 0

solve the rest quadratic equations

Step-by-step explanation:

Answer 2

Answer:

Step-by-step explanation:

sn+16=256

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

a=9,d=2

n/2[18(n-1)2]=256