Question Details

Let point (h, k) lies on x2 + y2 = 4 and point (2h + 1 , 3k + 2) lies on ellipse having eccentricity e. Then the value of 5 / e2 is ______.

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Correct Answer :

9

Solution :

The correct answer is 9.

Given that the point (h,k) lies on the circle x2+y2=4, we have:
h2+k2=4

Let (X,Y) represent the coordinates of the point lying on the ellipse, such that:
X=2h+1
and
Y=3k+2

We can express h and k in terms of X and Y respectively:
h=X-12
k=Y-23

Substituting these expressions into the equation h2+k2=4 gives:
X-122+Y-232=4

Simplifying the denominators:
(X-1)24+(Y-2)29=4

Dividing the entire equation by 4, we obtain the standard equation of the ellipse:
(X-1)216+(Y-2)236=1

Comparing this with the general equation of a shifted ellipse (x-x0)2a2+(y-y0)2b2=1, we identify the parameters:
a2=16
b2=36

Since b2>a2, the ellipse is vertically oriented, and the relation for its eccentricity e is given by:
a2=b2(1-e2)

Substituting the values of a2 and b2:
16=36(1-e2)
1-e2=1636
1-e2=49
e2=1-49=59

Finally, calculating the required value:
5e2=55/9=9

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