MHT CET2011MathematicsParabola
The equation of the common tangent touching the circle (x-3)²+y²=9 and the parabola y²=4 x above the x -axis is
Options
- A2 y=3 x+1
- B3 y=-(x+3)
- C3 y=x+3
- D3 y=-(3 x+1)
Correct answer
C. 3 y=x+3
Step-by-step solution
Let the common tangent to the parabola array l y²=4 x be y=m x+ 1 m array It should be also touch the circle (x-3)²+y²=9 whose centre is (3,0) and radius =3 , then array cc & |3 m+1 / m| 1+m² =3 & 3 m²=1 & m= 1 3 array But m>0 , then equation of common tangent is y= 1 3 x+ 3 or 3 y=x+3