Question

an=4,d=2,sn=-14 find n and a
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Answer 1

Answer:

A=-8 N=7

Step-by-step explanation:

a  n  =a+(n−1)d

4=a+(n−1)2

4=a+2n−2

6=a+2n

∴a=6−2n...(1)

S  n  =  2 n

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[2a+(n−1)d]

−14=  2 n

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[2(6−2n)+(n−1)2]

−28=n[12−4n+2n−2]

−28=12n−2n  2 −2n

−28=10n−2n  2

 

−14=5n−n  2

 

Solving the above equation, we get,

(n−7)(n+2)=0

n=7,−2

∴n=7

a=6−2n  From (1)

a=6−2(7)=−8

Answer 2

Step-by-step explanation:

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