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2015-02-13T15:00:56+05:30

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So using formula for a GP with first term a and common difference r

we have nth term = ar^{n-1}

so 6 th term is 8 times third term 

so ar⁵ = 8ar²

⇒ r = 2 


the sum of its first two terms

a + ar = 42 

⇒ a(1 + 2) = 42 

⇒ a = 14 

so the GP is 

14 , 28, 56 .......

2 3 2
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2015-02-13T15:07:58+05:30

This Is a Certified Answer

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Certified answers contain reliable, trustworthy information vouched for by a hand-picked team of experts. Brainly has millions of high quality answers, all of them carefully moderated by our most trusted community members, but certified answers are the finest of the finest.
General formula:

a,ar,a r^{2} ,a r^{3} ,......

So the third term : a r^{2}

6th term = a r^{5}

a r^{2} = 8a r^{2}
 r^{3}=8
r=2

a + ar = 42 
a+a(2) = 42
3a=42
a=14

GP= 14,14(2),14( 2^{2} ),......
GP=14 , 28, 56.......
2 3 2