1.

The 5term of anAs is40 and the10term is 20 how many term of the sequence make the sum zero​

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Answer:

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Step-by-step explanation:

(a) X

5

=40,x

10

=20

x

10

−x

5

=5d

5d=20−40=−20

⇒d=−4

Now, x

15

=x

10

+5d=20−20=0

(b) FIRST term, f=x

5

−4d=40−4(−4)=56

S

n

=

2

n[2f+(n−1)d]

⇒0=

2

n[2×56+(n−1)(−4)]

⇒n(112−4n+4)=0

⇒n(116−4n)=0

⇒=0,n=29

Thus, 29 terms of this sequence make the sum zero.


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