Question

Determine k so that 8k + 4,6k-2, and 2k -
7 are the three consecutive terms of the AP.
Which term of the AP 3, 6, 9, ....... gives
729.
Find the sum of the first 18 terms of the
AP 11, 8,5, 3 .......​

Answer 1

Answer:

Step-by-step explanation:

8k + 4,6k-2, and 2k - 7 are in AP

so 6k-2-(8k+4)=2k-7-(6k-2)

6k-2-8k-4=2k-7-6k+2

-2k-6=-4k-5

2k=1,k=1/2

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3, 6, 9, ....... gives  729.

a=3,d=3,an=729,n=?

an=a+(n-1)d

729=3+(n-1)*3

3+3n-3=729

3n=729

n=729/3=243

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11,8,5,3,....

a=11,d=-3,n=18

S18=18/2[(2*11+17*(-3)]

=9(22-51)

=9*(-29)

=-261

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