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The circle `x^(2)+y^(2)-8x=0` and hyperbola `(x^(2))/(9)-(y^(2))/(4)=1` intersect at the points `A` and `B`. The equation of a common tangent with positive slope to the circle as well as to the hyperbola, isA. `2x-sqrt(5)y-20=0`B. `2x-sqrt(5)y+4=0`C. `3x-4y+8=0`D. `4x-3y+4=0` |
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Answer» The equation of a tangent of slope `m` to the hyperbola `(x^(2))-(9)-(y^(2))/(4)=1` is `y=mx+sqrt(9m^(2)-4)` If it touches the circle `x^(2)+y^(2)-8x=0`, then `|(4m+sqrt(9m^(2)-4))/(sqrt(1+m^(2)))|=4` `implies495m^(4)+104m^(2)-400=0` `implies(5m^(2)-4)(99m^(2)+100)=0` `impliesm^(2)=(4)/(5)=(2)/(sqrt(5))` Substituting the value of `m` in `(i)`, we get `2x-sqrt(5)y+4=0` as the equation of the required common tangent |
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