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MathsMediumNumerical2021 · 27 Jul Shift 2

Q84.Let E be an ellipse whose axes are parallel to the co-ordinates axes, having its centre at (3, −4), one focus at (4, −4) and one vertex at (5, −4). If mx −y = 4, m > 0 is a tangent to the ellipse E, then the value of 5m2 is equal to _____ .

What This Question Tests

This question requires determining the equation of an ellipse from its given center, focus, and vertex, and then applying the condition for a line to be tangent to the ellipse to find an unknown parameter.

Concepts Tested

Equation of an ellipseProperties of ellipse (center, focus, vertex)Condition for tangency of a line to an ellipse

Formulas Used

Equation of ellipse: (x-h)^2/a^2 + (y-k)^2/b^2 = 1

c = ae

b^2 = a^2(1-e^2)

Condition for tangency y=mx+c to x^2/a^2 + y^2/b^2 = 1 is c^2 = a^2m^2 + b^2

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