If the line y = m x + 7 3 is normal to the hyperbola x 2 24 - y 2 18 = 1 , then a value of m is:

If the line y=mx+73 is normal to the hyperbola x224-y218=1, then a value of m is:
  1. 52
  2. 35
  3. 152
  4. 25

Solution

The given equation of the hyperbola is x224-y218=1, which is of the form x2a2-y2b2=1.

a2=24; b2=18

We know that the equation of a normal of slope m to the hyperbola x2a2-y2b2=1 is y=mx±ma2+b2a2-b2m2

Thus, the equation of the normal to the given hyperbola is y=mx±m24+1824-18m2

y=mx±m4224-18m2

Given, the normal is y=mx+73

Hence, comparing the two equations, we get 42m24-18m2=73

 42m224-18m2=49×3

 42×42m2=49×324-18m2

 12m2=24-18m2

 m2=2430=45

 m=±45=±25.

Asked in: JEE Main 2019 (09 Apr Shift 1)

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