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Question

If p, $g_1$, $g_2$ and q are in GP and m is the arithmetic mean of p and q, then $\frac{g_1^2}{g_2} + \frac{g_2^2}{g_1}$ is equal to

The correct answer is
2m

Geometric Progression (GP) and Arithmetic Mean (AM) Problem

The question asks for the value of the expression $\frac{g_1^2}{g_2} + \frac{g_2^2}{g_1}$, given that p, $g_1$, $g_2$, and q are terms in a Geometric Progression (GP), and m is the Arithmetic Mean (AM) of p and q.

GP Properties Analysis

Let the first term of the GP be p and the common ratio be r.

  • Since p, $g_1$, $g_2$, q are in GP, we can express the terms as:
    • $g_1 = p \cdot r$
    • $g_2 = p \cdot r^2$
    • $q = p \cdot r^3$

Simplifying the Expression

Now, substitute these terms into the expression $\frac{g_1^2}{g_2} + \frac{g_2^2}{g_1}$:

  • Calculate the first part: $ \frac{g_1^2}{g_2} = \frac{(p \cdot r)^2}{p \cdot r^2} = \frac{p^2 \cdot r^2}{p \cdot r^2} = p $
  • Calculate the second part: $ \frac{g_2^2}{g_1} = \frac{(p \cdot r^2)^2}{p \cdot r} = \frac{p^2 \cdot r^4}{p \cdot r} = p \cdot r^3 $
  • Recognize that $p \cdot r^3$ is equal to the fourth term, q.
  • So, the expression simplifies to: $ \frac{g_1^2}{g_2} + \frac{g_2^2}{g_1} = p + q $

Relating to Arithmetic Mean (AM)

The problem states that m is the Arithmetic Mean (AM) of p and q.

  • By definition of AM: $ m = \frac{p+q}{2} $
  • Rearranging this formula gives: $ p+q = 2m $

Final Calculation

Substitute the value of $p+q$ back into the simplified expression:

  • $ \frac{g_1^2}{g_2} + \frac{g_2^2}{g_1} = p + q = 2m $

Therefore, the value of the expression is $2m$.

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Important Questions from Geometric Progressions

  1. If \(2^{\frac{1}{c}}, 2^{\frac{b}{a c}}, 2^{\frac{1}{a}}\) are in GP, then which one of the following is correct ?

  2. If G is the geometric mean of numbers 1, 2, 22, 23,.....2n-1, then what is the value of 1 + 2log2G ?

  3. If m is the geometric mean of \({\left( {\frac{{\rm{y}}}{{\rm{z}}}} \right)^{\log \left( {{\rm{yz}}} \right)}},{\rm{\;}}{\left( {\frac{{\rm{z}}}{{\rm{x}}}} \right)^{\log \left( {{\rm{zx}}} \right)}}{\rm{\;and\;}}{\left( {\frac{{\rm{x}}}{{\rm{y}}}} \right)^{\log \left( {{\rm{xy}}} \right)}}\) then what is the value of m?

  4. The value of the infinite product \({6^{\frac{1}{2}}} \times {6^{\frac{1}{2}}} \times {6^{\frac{3}{8}}} \times {6^{\frac{1}{4}}} \times \ldots \) is

  5. The geometric mean of the observations x 1, x 2, x 3, … x nis G 1. The geometric mean of the observations y 1, y 2, y 3,… y nis G 2. The geometric mean of observations \(\frac{{{{\rm{x}}_1}}}{{{{\rm{y}}_1}}},\frac{{{{\rm{x}}_2}}}{{{{\rm{y}}_2}}},\frac{{{{\rm{x}}_3}}}{{{{\rm{y}}_3}}}, \ldots \frac{{{{\rm{x}}_{\rm{n}}}}}{{{{\rm{y}}_{\rm{n}}}}}\) is

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