Question

if 6th and 9th term of geometrical sequence are 1 and 8 respectively which term of the sequence is 64?
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Answer 1

Answer:

11th term of gp is 64

Step-by-step explanation:

t6= ar^5= 1 (i)

t9= ar^8 =8 (ii)

a = 1/r^5 from (i)

a= 8/r^8 from (ii)

from (i) and (ii)

1/r^5 = 8/r^8

by solving this, we get

r³=8

r = 2 (iii)

putting value of r in equation no. (i)

we get value of a = 1/32

now, we know that

tn= ar^n-1

64= 1/32 × 2^n

64×32= 2^n

2048= 2^n

2^11 = 2^n

n=11 (same base and power equal)

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