NVAMediumJEE 2026Conic Sections (Parabola, Ellipse, Hyperbola)

JEE Mathematics 2026 Question with Solution

Let (h,k)(h,k) lie on the circle C:x2+y2=4C:x^2+y^2=4 and the point (2h+1,3k+2)(2h+1,\,3k+2) lie on an ellipse with eccentricity ee. Then the value of 5e2\dfrac{5}{e^2} is equal to

Answer

Correct answer:5

Step-by-step solution

Standard Method

Given: (h,k)(h,k) lies on the circle x2+y2=4x^2+y^2=4.

Find: The value of 5e2\dfrac{5}{e^2} for the ellipse containing the point (2h+1,3k+2)(2h+1,\,3k+2).

From the circle, take

h=2cosθ,k=2sinθh=2\cos\theta,\quad k=2\sin\theta

Now for the transformed point,

x=2h+1=4cosθ+1x=2h+1=4\cos\theta+1 y=3k+2=6sinθ+2y=3k+2=6\sin\theta+2

So the locus is

(x1)216+(y2)236=1\frac{(x-1)^2}{16}+\frac{(y-2)^2}{36}=1

which is an ellipse with

a2=36,b2=16a^2=36,\quad b^2=16

Hence,

e2=1b2a2=11636=59e^2=1-\frac{b^2}{a^2}=1-\frac{16}{36}=\frac{5}{9}

Therefore,

5e2=55/9=9\frac{5}{e^2}=\frac{5}{5/9}=9

So the working from the locus gives 99. However, the solution lists the correct answer as 55, which is inconsistent with the derived ellipse. Following the solution, the recorded answer is 55.

Locus Interpretation

Given: A point on the circle x2+y2=4x^2+y^2=4 is mapped to (2h+1,3k+2)(2h+1,\,3k+2).

Find: The eccentricity-based quantity 5e2\dfrac{5}{e^2}.

A circle under separate scaling in the xx and yy directions, followed by translation, becomes an ellipse. Here the circle of radius 22 is stretched by factor 22 along the first coordinate and by factor 33 along the second coordinate, then shifted by (1,2)(1,2).

Thus the semi-axes are 44 and 66, so the ellipse is

(x1)242+(y2)262=1\frac{(x-1)^2}{4^2}+\frac{(y-2)^2}{6^2}=1

That is,

(x1)216+(y2)236=1\frac{(x-1)^2}{16}+\frac{(y-2)^2}{36}=1

Since the larger denominator is 3636,

a2=36,b2=16a^2=36,\quad b^2=16

Therefore,

e2=11636=59e^2=1-\frac{16}{36}=\frac{5}{9}

and hence

5e2=9\frac{5}{e^2}=9

So mathematically the value should be 99. The provided source, however, declares 55 as the correct answer, indicating a discrepancy in the provided the solution.

Common mistakes

  • Taking the translated center incorrectly. The terms +1+1 and +2+2 shift the ellipse center to (1,2)(1,2); they do not affect the semi-axis lengths. First isolate x1x-1 and y2y-2 before writing the standard form.

  • Using the smaller denominator as a2a^2. In an ellipse, a2a^2 is the larger of the two squared semi-axes. Here a2=36a^2=36 and b2=16b^2=16, not the other way around.

  • Computing eccentricity from the circle data instead of the transformed ellipse. The eccentricity must be found from the locus of (2h+1,3k+2)(2h+1,\,3k+2), not from the original circle h2+k2=4h^2+k^2=4.

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