Hyperbola 2 Question 4

4. The equation of a tangent to the hyperbola 4x25y2=20 parallel to the line xy=2 is

(a) xy3=0

(b) xy+9=0

(c) xy+1=0

(d) xy+7=0

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Answer:

Correct Answer: 4. (b)

Solution:

  1. Given equation of hyperbola is

4x25y2=20

which can be rewritten as

x25y24=1

The line xy=2 has slope, m=1

Slope of tangent parallel to this line =1

We know equation of tangent to hyperbola x2a2y2b2=1 having slope m is given by

y=mx±a2m2b2

Here, a2=5,b2=4 and m=1

Required equation of tangent is

y=x±54y=x±1xy±1=0



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