Question

Sum of 2nd and 3rd terms of a G.P. is 3 and sum of next two is 12 ; find the first term.​

Answer 1

Answer:

Down vote

So you have that

ar+ar2=12ar2+ar3=60

Then

a=12r+r2ar2+ar3=60

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a=12r+r212r+r2r2+12r+r2r3=60

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12r+r2r2+12r+r2r3=6012r+r2r+r212

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12r2+12r3=60(r+r2)

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12r3−48r2−60r=0

⟹

12r2−48r−60=0

$ Now solve this equation and you will find 2 solutions. Then you should verify which one satisfies the first equation

Explanation

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