Question

how many terms of ap -15 -13 -11....are nedeed to make sum -55

Answer 1

Answer:sorry I don't know the answer

Step-by-step explanation:

Answer 2

Sn = n/2{2a+(n-1)d}

-55=n/2{2(-15)+(n-1)2}

-110=n{-30+2n-2}

-110=n{-32+2n}

-110=-32n + 2n²

2n² - 32n + 110 = 0

n²-16n+55=0

n²-11n-5n+55=0

n(n-11) - 5(n-11)=0

(n-11)(n-5)=0

n=11 or 5

•^• n = 11 or 5