MHT CET202523 Apr 2025Evening ShiftMathematicsApplication of DerivativesActual
If the line a x+ by + c =0 is normal to the curve x y =1 , then
Options
- Aa>0, b>0
- Ba>0, b < 0
- Ca < 0, b 0
- Da < 0, b < 0
Correct answer
B. a>0, b < 0
Step-by-step solution
Given the line ax + by + c = 0 is normal to the curve xy = 1 , we determine the required relationship between a and b . Find the derivative of xy = 1 using implicit differentiation: y + x dy dx = 0 , so dy dx = - y x . The slope of the normal is the negative reciprocal of the tangent slope: m_N = x y . The slope of the line ax + by + c = 0 is m_L = - a b . Equating slopes since the line is normal: - a b = x y . On the curve xy = 1 , x and y are non-zero and share the same sign, so x y > 0 . Thus, - a b > 0 , implyi