How many
27, 24, 21,
so that
terms of the AP
should be taken
their sum
is zero2
2
Answers
Answered by
2
Step-by-step explanation:
Here, a = 27, d = - 3, Sn = 0
Let first term be
a
=
27
a=27
And common difference be
d
=
−
3
d=−3
According to question, sum is zero,
⟹
n
2
[
2
a
+
(
n
−
1
)
d
]
=
0
⟹n2[2a+(n−1)d]=0
⟹
[
54
+
(
n
−
1
)
(
−
3
)
]
=
0
⟹[54+(n−1)(−3)]=0
⟹
n
=
19
⟹n=19
Hence,
19
19 terms of AP should be taken to make sum zero.
Value of the last term, i.e;
a
19
=
a
+
(
19
−
1
)
d
a19=a+(19−1)d
⟹
a
19
=
27
+
(
18
)
(
−
3
)
⟹a19=27+(18)(−3)
⟹
a
19
=
−
27
⟹a19=−27
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