Which term in the A.P 121,117,113.... is the first -ve term
Answers
Answered by
4
first negative term is -1
an=-1
a=121
d=-4
n=?
an=a+(n-1)d
-1=121+(n-1)(-4)
-122/-4=n-1
n-1=30.5
n-1=31....(approx)
n=32
32nd term is first negative term of the A.P
hope it helps
an=-1
a=121
d=-4
n=?
an=a+(n-1)d
-1=121+(n-1)(-4)
-122/-4=n-1
n-1=30.5
n-1=31....(approx)
n=32
32nd term is first negative term of the A.P
hope it helps
SamyakShrestha:
how are you sure that -1 is the first negative term?? can you explain the process
not like that, the first negative term in the numbers is -1 so that the first negative term of the ap will be -1 or after -1 . so we assume
but, how is that even logical
what if the difference was like -21 instead of -4. you can't say just find it using ''hit and trial'' right?
no you can use this way just put '>' in '=' place
Answered by
3
a=121
d=-4
n=?
tn=x <0
now,
a+(n-1)d<0
121+(n-1)(-4)<0
121-4n+4<0
125-4n <0
125-4n+4n <4n
125 <4n
125/4 <n [dividing all sides by 4]
31.25 <n
since n must be a whole no., the whole no. just greater than 31.25 is 32( since n>31.25)
so,
a+(n-1)d
=121+(32-1)(-4)
=121+31 (-4)
=121-124
=-3
d=-4
n=?
tn=x <0
now,
a+(n-1)d<0
121+(n-1)(-4)<0
121-4n+4<0
125-4n <0
125-4n+4n <4n
125 <4n
125/4 <n [dividing all sides by 4]
31.25 <n
since n must be a whole no., the whole no. just greater than 31.25 is 32( since n>31.25)
so,
a+(n-1)d
=121+(32-1)(-4)
=121+31 (-4)
=121-124
=-3
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