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Consider the function \(f(x, y) = \dfrac{x^{2}}{2} + \dfrac{y^{2}}{3} - 5\). All the roots of this function

  • A.form a finite set of points.
  • B.lie on an elliptical curve.
  • C.lie on the surface of a sphere.
  • D.lie on a hyperbolic curve.

Answer: B

The roots lie on an elliptical curve.

The roots are the points where \(f(x, y) = 0\):

\[ \begin{aligned} \frac{x^{2}}{2} + \frac{y^{2}}{3} &= 5 \\ \frac{x^{2}}{10} + \frac{y^{2}}{15} &= 1 \end{aligned} \]

This is an ellipse in the xy-plane with semi-axes \(\sqrt{10}\) along x and \(\sqrt{15}\) along y.

An ellipse has infinitely many points, so the roots are not a finite set. A sphere would need three variables, and the function has only two. A hyperbola would need the two squared terms to have opposite signs, but both are positive here.

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