Mathematics - Sequence & Series Question with Solution | TestHub

MathematicsSequence & SeriesG.P.Medium2 minPYQ_2020

MathematicsMediumstatement

The sum of the first three terms of $G . P$ is $S$ and their products is $27$ . Then all such $S$ lie in

Answer:

Solution:

Let terms are $\frac{a}{r}, a, a r$

then $a^{3} = 27 \Rightarrow a = 3$

Now $S = \frac{3}{r} + 3 + 3 r$

$S = 3 (\frac{1}{r} + r) + 3$

$r + \frac{1}{r} \geq 2 \forall r > 0$ or $r + \frac{1}{r} \leq - 2 \forall r < 0$

$S \in (- \infty, - 3] \cup [9, \infty)$

Stream:JEESubject:MathematicsTopic:Sequence & SeriesSubtopic:G.P.

⏱ 2mℹ️ Source: PYQ_2020

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