COMEDK2013MathematicsApplication of Derivatives
If a tangent to the curve y=6 x-x² is parallel to the line 4 x-2 y-1=0 , then the point of tangency on the curve is
Options
- A(2,8)
- B(8,2)
- C(6,1)
- D(4,2)
Correct answer
A. (2,8)
Step-by-step solution
Let P (x₁, y₁ ) be the required point. The given curve is aligned y &=6 x-x² d i j d x &=6-2 x ( d y d x )_ (x₁, h ) &=6-2 x₁ aligned Since, the tangent at (x₁, y₁ ) is parallel to the line 4 x-2 y-1=0 . Slope of the tangent at (x₁, y₁ )= Slope of the line 4 x-2 y-1=0 ( d y d x )_ (x, b) =2 6-2 x₁=2 x₁=2 y₁=6 x₁-x₁²=6 2-2²=8 Thus, required point is (2,8) .