



 
Hi Muhammad, Suppose the infinite geometric series is \[a + ar + ar^2 + ar^3 \cdot \cdot \cdot\] If the series converges then its sum is $\large \frac{a}{1  r}.$ This sum you know is 15. Now square each term to get the infinite geometric series \[a^2 + a^2 r^2 + a^2 r^4 \cdot \cdot \cdot\] What is the sum of this series? You know the value is 45. This gives you two equations in $a$ and $r.$ Solve for $a$ and $r.$ Penny  


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