Question

how many terms of Ap -5,-7,-9… will make the sum -140​

Answer 1

Answer:

10

Step-by-step explanation:

given

a=-5

d=-2

S=-140

formula

S = (n/2) × (2a + (n−1)d)

substitute given values in the above formula

-140=(n/2) × (2×-5+ (n−1)-2)

-280=(n) × (-10-2n+2)

-280=n×(-8-2n)

280=8n+2n^2

140=4n+n^2

n^2+4n-140=0

by solving the above quadratic equation we get

n=10,-14

as n cannot be negative value

n should be 10

finally sum of 10 terms in Ap gives -140

Answer 2

Answer:

10 terms

hope it helps

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