Answered Oct 12, 2017

A= 121

d= -4

let the first negative term be an,

s0 an<0

a+(n-1)d<0

121+(n-1)(-4)<0

121-4n+4<0

125-4n<0

so by hit and trial method,

let n=30,so 125-4n

=125-120=5,which is not less than0

again let n=31

so 125-4n=125-124=1 which is not less than 0

now,let n=32 so 125-4n=125-128= -3 hence the first negetive term is -3

now an= -3

a+(n-1)d= -3

121+(n-1)(-4)= -3

-4(n-1)= -3-121

-4(n-1)=-124

n-1=32

n=33

hence,answer is 33

Answered Sep 17, 2017

Replied on Oct 12, 2017

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