NTA Abhyas JEE Main2020MathematicsContinuity and DifferentiabilityPractice
If f(x) = λ 2 x + 3 , 0 ≤ x ≤ 3 μ x + 12, 3 < x ≤ 9 is differentiable at x = 3 , then the value of λ + μ is equal to
Correct answer
8
Step-by-step solution
∵ f ( x ) is continuous at x = 3 ∴ L H L = R H L = f ( 3 ) λ 2 ( 3 ) + 3 = μ ( 3 ) + 12 ⇒ λ = μ +4 ......(1) Also f ( x ) is differentiable at x = 3 ∴ at x = 3 L H D = R H D λ 2 2 ( 3 ) + 3 · 2 = μ ⇒ λ = 3 μ ......(2) By (1) and (2) μ = 2 , λ = 6