Question:medium

The sum of two numbers is 6 times their geometric mean, show that numbers are in the ratio (3+2√2) : (3-2√2).

Updated On: Jan 21, 2026
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Solution and Explanation

Let the two positive numbers be a and b.

It is given that the sum of the two numbers is 6 times their geometric mean.

∴ \[ a + b = 6\sqrt{ab} \]

Squaring both sides, we get \[ (a + b)^2 = 36ab \]

\[ a^2 + b^2 + 2ab = 36ab \]

\[ a^2 + b^2 - 34ab = 0 \quad \text{… (1)} \]

Dividing equation (1) by \( b^2 \), we get \[ \left(\frac{a}{b}\right)^2 - 34\left(\frac{a}{b}\right) + 1 = 0 \]

Let \( \frac{a}{b} = x \). Then, \[ x^2 - 34x + 1 = 0 \]

Solving the quadratic equation: \[ x = \frac{34 \pm \sqrt{34^2 - 4}}{2} \]

\[ x = \frac{34 \pm \sqrt{1156 - 4}}{2} \]

\[ x = \frac{34 \pm \sqrt{1152}}{2} \]

\[ x = \frac{34 \pm 24\sqrt{2}}{2} \]

\[ x = 17 \pm 12\sqrt{2} \]

Therefore, \[ \frac{a}{b} = 17 + 12\sqrt{2} \quad \text{or} \quad 17 - 12\sqrt{2} \]

Dividing numerator and denominator by 1, we write the ratio as \[ a : b = (17 + 12\sqrt{2}) : 1 \]

Taking square roots on both sides of the original ratio form, we get the ratio of the numbers as

\[ (3 + 2\sqrt{2}) : (3 - 2\sqrt{2}) \]

Hence, the two numbers are in the ratio \[ (3 + 2\sqrt{2}) : (3 - 2\sqrt{2}). \]

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