Q63
Geometric Sequences and Series
Sum of an Infinite Geometric Series (Direct Computation)
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If the sum of an infinite GP, $a , a r , a r ^ { 2 } , a r ^ { 3 } , \ldots$ is 15 and the sum of the squares of its each term is 150 , then the sum of $a r ^ { 2 } , a r ^ { 4 } , a r ^ { 6 } , \ldots$ is:
(1) $\frac { 25 } { 2 }$
(2) $\frac { 9 } { 2 }$
(3) $\frac { 1 } { 2 }$
(4) $\frac { 5 } { 2 }$