Question:medium

The points on the curve \(xy^2 = 1\) which are nearest to the origin, are

Show Hint

For distance minimization problems, minimize the square of the distance to avoid square roots.
Updated On: May 24, 2026
  • \(\left(\frac{1}{2^{1/3}}, \pm 2^{1/6}\right)\)
  • \(\left(\frac{1}{2^{1/3}}, \pm 2^{-1/6}\right)\)
  • \(\left(2^{1/3}, \pm \frac{1}{2^{1/6}}\right)\)
  • None of these
Show Solution

The Correct Option is A

Solution and Explanation

To determine which points on the curve \(xy^2 = 1\) are nearest to the origin, we need to minimize the distance from a point \((x, y)\) on this curve to the origin \((0, 0)\). The distance \(D\) from a point \((x, y)\) to the origin is given by the formula:

\(D = \sqrt{x^2 + y^2}\)

Since we are minimizing, it is often easier to minimize the square of the distance to avoid dealing with the square root. So we minimize:

\(D^2 = x^2 + y^2\)

Given the constraint \(xy^2 = 1\), we express \(y\) in terms of \(x\):

\(y^2 = \frac{1}{x}\)

Hence, \(y = \pm \sqrt{\frac{1}{x}}\).

Substitute \(y^2\) into the equation to express \(D^2\) entirely in terms of \(x\):

\(D^2 = x^2 + \frac{1}{x}\)

To find the minimum value of \(D^2\), we differentiate it with respect to \(x\) and set the derivative to zero.

\(\frac{d}{dx}(D^2) = 2x - \frac{1}{x^2}\)

Setting \(\frac{d}{dx}(D^2) = 0\), we have:

\(2x - \frac{1}{x^2} = 0\)

This implies:

\(2x^3 = 1\)

Solving for \(x\), we get:

\(x = \frac{1}{2^{1/3}}\)

Substitute \(x = \frac{1}{2^{1/3}}\) back into the expression for \(y\):

\(y = \pm \sqrt{\frac{1}{x}} = \pm \sqrt{2^{1/3}} = \pm 2^{1/6}\)

Hence, the points on the curve closest to the origin are:

\(\left(\frac{1}{2^{1/3}}, \pm 2^{1/6}\right)\)

Thus, the correct answer is:

\(\left(\frac{1}{2^{1/3}}, \pm 2^{1/6}\right)\)

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