How Do You Solve a Geometric Progression with Sum and Term Constraints?

[jinx007]

An infinite geometric progression has a finite sum. Given that the sum of the first two terms is 9 and the third term is 12.

1/ Find the value of the first term and the common ration r.

 

[thrill3rnit3]

Work shown?

 

[jinx007]

Work shown?

what? i cannot really understand what you r saying
i just need help..lolzz...in fact don't really know where to start..y the way i know the equation

 

[thrill3rnit3]

what? i cannot really understand what you r saying
i just need help..lolzz...in fact don't really know where to start..y the way i know the equation

Well, I can't just spoonfeed you with the answer.

A geometric progression can be written as a, ar, ar², ar³,..., arⁿ

Where a is the first term, and r is the common ratio

If the sum of the first two terms is 9, we can rewrite that as

a + ar = 9

If the third term is 12, we can rewrite it as

ar² = 12

Now you have 2 equations in 2 unknowns. I think it should be solvable now.