Conic Sections (Hyperbola) NCERT Solutions Exercise 10.4 Class 11 Math (Set-2)


NCERT Question 7 : Find the equation of the hyperbola with vertices $(\pm 2, 0)$ and foci $(\pm 3, 0)$.

Solution:
Since the foci lie on the x-axis, the equation of the hyperbola is of the form
$$\frac{x^2}{a^2} – \frac{y^2}{b^2} = 1$$

Given, vertices $(\pm 2, 0)$ and foci $(\pm 3, 0)$

So,
$$a = 2, \quad c = 3$$

We know that
$$c^2 = a^2 + b^2$$

$$b^2 = c^2 – a^2 = 9 – 4 = 5$$

Hence, the equation is
$$\frac{x^2}{4} – \frac{y^2}{5} = 1$$


NCERT Question 8 : Find the equation of the hyperbola with vertices $(0, \pm 5)$ and foci $(0, \pm 8)$.

Solution:
Since the foci lie on the y-axis, the equation of the hyperbola is of the form
$$\frac{y^2}{a^2} – \frac{x^2}{b^2} = 1$$

Given, vertices $(0, \pm 5)$ and foci $(0, \pm 8)$

So,
$$a = 5, \quad c = 8$$

We know that
$$b^2 = c^2 – a^2 = 64 – 25 = 39$$

Hence, the equation is
$$\frac{y^2}{25} – \frac{x^2}{39} = 1$$


NCERT Question 9 : Find the equation of the hyperbola with vertices $(0, \pm 3)$ and foci $(0, \pm 5)$.

Solution:
Since the foci lie on the y-axis, the equation of the hyperbola is of the form
$$\frac{y^2}{a^2} – \frac{x^2}{b^2} = 1$$

Given, vertices $(0, \pm 3)$ and foci $(0, \pm 5)$

So,
$$a = 3, \quad c = 5$$

We know that
$$b^2 = c^2 – a^2 = 25 – 9 = 16$$

Hence, the equation is
$$\frac{y^2}{9} – \frac{x^2}{16} = 1$$


NCERT Question 10 : Find the equation of the hyperbola whose foci are $(\pm 5, 0)$ and whose transverse axis is of length $8$.

Solution:
Since the foci lie on the x-axis, the equation of the hyperbola is of the form
$$\frac{x^2}{a^2} – \frac{y^2}{b^2} = 1$$

Given, $c = 5$ and length of the transverse axis $= 8 \Rightarrow 2a = 8$
So,
$$a = 4$$

Now,
$$b^2 = c^2 – a^2 = 25 – 16 = 9$$

Hence, the equation is
$$\frac{x^2}{16} – \frac{y^2}{9} = 1$$


NCERT Question 11 : Find the equation of the hyperbola whose foci are $(0, \pm 13)$ and the conjugate axis is of length $24$.

Solution:
Since the foci lie on the y-axis, the equation of the hyperbola is of the form
$$\frac{y^2}{a^2} – \frac{x^2}{b^2} = 1$$

Given, $c = 13$ and length of conjugate axis $= 24 \Rightarrow 2b = 24$
So,
$$b = 12$$

Now,
$$a^2 = c^2 – b^2 = 169 – 144 = 25$$

Hence, the equation is
$$\frac{y^2}{25} – \frac{x^2}{144} = 1$$


NCERT Question 12 : Find the equation of the hyperbola whose foci are $(\pm 3\sqrt{5}, 0)$ and whose latus rectum is of length $8$.

Solution:
Since the foci lie on the x-axis, the equation of the hyperbola is of the form
$$\frac{x^2}{a^2} – \frac{y^2}{b^2} = 1$$

Given, $c = 3\sqrt{5}$ and latus rectum $= 8$.

We know,
$$\text{Latus rectum} = \frac{2b^2}{a} = 8$$
So,
$$b^2 = 4a \quad \text{…(1)}$$

Also,
$$c^2 = a^2 + b^2$$

$$45 = a^2 + 4a$$

$$a^2 + 4a – 45 = 0$$

Solving,
$$(a + 9)(a – 5) = 0$$

Since $a > 0$, we take $a = 5$.
Substitute in (1):
$$b^2 = 4a = 20$$

Hence,
$$a^2 = 25, \quad b^2 = 20$$

The equation is
$$\frac{x^2}{25} – \frac{y^2}{20} = 1$$


NCERT Question 13 : Find the equation of the hyperbola whose foci are $(\pm 4, 0)$ and whose latus rectum is of length $12$.

Solution:
Since the foci lie on the x-axis, the equation of the hyperbola is of the form
$$\frac{x^2}{a^2} – \frac{y^2}{b^2} = 1$$

Given, $c = 4$ and latus rectum $= 12$.

We know,
$$\frac{2b^2}{a} = 12 \Rightarrow b^2 = 6a \quad \text{…(1)}$$

Also,
$$c^2 = a^2 + b^2$$

$$16 = a^2 + 6a$$

$$a^2 + 6a – 16 = 0$$

Solving,
$$(a + 8)(a – 2) = 0$$

Hence, $a = 2$ (since $a > 0$).
Substituting in (1):
$$b^2 = 6(2) = 12$$

Thus,
$$a^2 = 4, \quad b^2 = 12$$

The equation is
$$\frac{x^2}{4} – \frac{y^2}{12} = 1$$


NCERT Question 14 : Find the equation of the hyperbola with vertices $(\pm 7, 0)$ and eccentricity $e = \frac{4}{3}$.

Solution:
Since the vertices lie on the x-axis, the equation of the hyperbola is of the form
$$\frac{x^2}{a^2} – \frac{y^2}{b^2} = 1$$

Given, $a = 7$ and $e = \frac{4}{3}$.

We know,
$$e = \frac{c}{a} \Rightarrow c = ea = \frac{4}{3} \times 7 = \frac{28}{3}$$

Now,
$$b^2 = c^2 – a^2 = \frac{784}{9} – 49 = \frac{784 – 441}{9} = \frac{343}{9}$$

Hence,
$$a^2 = 49, \quad b^2 = \frac{343}{9}$$

The equation is
$$\frac{x^2}{49} – \frac{9y^2}{343} = 1$$


NCERT Question 15 : Find the equation of the hyperbola whose foci are $(0, \pm \sqrt{10})$ and which passes through the point $(2, 3)$.

Solution:
Since the foci lie on the y-axis, the equation of the hyperbola is of the form
$$\frac{y^2}{a^2} – \frac{x^2}{b^2} = 1$$

Given, $c = \sqrt{10}$ and the curve passes through $(2, 3)$.

We know,
$$b^2 = c^2 – a^2 = 10 – a^2 \quad \text{…(1)}$$

Substitute $(x, y) = (2, 3)$ in the equation:
$$\frac{3^2}{a^2} – \frac{2^2}{b^2} = 1$$

$$\frac{9}{a^2} – \frac{4}{10 – a^2} = 1$$

Simplify:
$$9(10 – a^2) – 4a^2 = a^2(10 – a^2)$$

$$90 – 9a^2 – 4a^2 = 10a^2 – a^4$$

$$a^4 – 23a^2 + 90 = 0$$

Factoring,
$$(a^2 – 18)(a^2 – 5) = 0$$

Since $a < c$, we take $a^2 = 5$.
From (1),
$$b^2 = 10 – 5 = 5$$

Hence, the equation is
$$\frac{y^2}{5} – \frac{x^2}{5} = 1$$

Learn complete NCERT Class 11 Maths Chapter on Hyperbola with step-by-step solutions and conceptual insights from Anand Classes — ideal for JEE, NDA, and CUET preparation.


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