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The coordinates of foci of the hyperbola \(\rm \frac{x^2}{16} - \frac{y^2}{9} = 1\) is
1. (± 5, 0)
2. (± 4, 0)
3. (± 3, 0)
4. None of these

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Best answer
Correct Answer - Option 1 : (± 5, 0)

Concept:

Standard equation of an hyperbola: \(\frac{{{\rm{\;}}{{\bf{x}}^2}}}{{{{\bf{a}}^2}}} - \frac{{{{\bf{y}}^2}}}{{{{\bf{b}}^2}}} = 1\) (a > b)

  • Coordinates of foci = (± ae, 0)
  • Eccentricity (e) = \(\sqrt {1 + {\rm{\;}}\frac{{{{\rm{b}}^2}}}{{{{\rm{a}}^2}}}} \) ⇔ a2e2 = a2 + b2
  • Length of Latus rectum = \(\rm \frac{2b^2}{a}\)

 

Calculation:

Given: \(\rm \frac{x^2}{16} - \frac{y^2}{9} = 1\)

Compare with the standard equation of a hyperbola: \(\frac{{{\rm{\;}}{{\bf{x}}^2}}}{{{{\bf{a}}^2}}} - \frac{{{{\bf{y}}^2}}}{{{{\bf{b}}^2}}} = 1\)

So, a2 = 16 and b2 = 9

⇒ a = 4 and b = 3   (a > b)

Now, Eccentricity (e) = \(\sqrt {1 + {\rm{\;}}\frac{{{{\rm{b}}^2}}}{{{{\rm{a}}^2}}}} \) 

\(\sqrt {1 + \frac{9}{16}}\)

\(\sqrt { \frac{16+9}{16}}\)

\(\frac 54\)

Coordinates of foci = (± ae, 0) 

= (± 5, 0)

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