MHT CET2017MathematicsApplication of Derivatives
The point on the curve y = x - 1 where the tangent is perpendicular to the line 2 x + y - 5 = 0 is
Options
- A( 2 , − 1 )
- B( 10 , 3 )
- C( 2 , 1 )
- D( 5 , − 2 )
Correct answer
C. ( 2 , 1 )
Step-by-step solution
For given curve, d y d x = 1 2 x - 1 = m 1 (say) Now Slope of line 2 x + y - 5 = 0 is m 2 = - 2 Since lines are perpendicular ⇒ m 1 m 2 = - 1 ⇒ 1 2 x - 1 - 2 = - 1 ⇒ 2 2 x - 1 = 1 ⇒ x - 1 = 1 ⇒ Squaring both sides, x - 1 = 1 ⇒ x = 2 ⇒ y = x - 1 = 2 - 1 = 1 = 1 So the required point is 2 , 1