Question

how many terms of the ap -15, -13, -11..... needed to make the sum +55​

Answer 1

Step-by-step explanation:

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

110=n(2*-15+(n-1)*2)

110=n(-30+2n-2)

110=-32n+2n^2

55=-16n+n^2

n^2-16n-55=o

after doing factor

n-5=0

n=5

or

n-11=0

n=11

thanks

hope its helpful.....