AP EAMCET20224 Jul 2022Evening ShiftMathematicsContinuity and DifferentiabilityActual
If f x = 1 x ; x ≥ 1 a x 2 + b ; – 1 < x < 1 is differentiable ∀ x , then one of the value of a and b is-
Options
- Aa = 1 2 , b = – 3 2
- Ba = – 1 2 , b = 3 2
- Ca = 3 2 , b =   1 2
- DNone of these
Correct answer
B. a = – 1 2 , b = 3 2
Step-by-step solution
Given, f x   = 1 x ; x   ≥ 1 a x 2 + b ; – 1 < x < 1 ⇒ f x = - 1 x x ≤ - 1 a x 2 + b - 1 < x < 1 1 x x > 1 Also given funciton at x = 1 is continuous So, a . 1 + b = 1   . . . . . . 1 Also at x = 1 differentiable 2 a x = – 1 x 2 Now at x = 1 ⇒ 2 a = – 1 So, a = – 1 2 Now using equation 1 we get, b = 3 2 .