Answer:

Ans: A = 6 - 2(7) = -8.

Step-by-step explanation:

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

[2a+(n−1)d]

−14=

2

n

[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

Was this answer helpful?

Verified answer

Answer:

a+(n-1)d = An

10+ (n-1)6=100

(n-1)6=100-10

(n-1)=90/6

n-1=15 , n=15+1=16

value of n is 16

Sn= n/2(2a+(n-1)d

Sn= 16/2(2×10+(16-1)6

Sn= 8 ×55 = 880