If the function f(x)= cases 1|x|, & |x| 2 \ ax2+2b, & |x|<2 cases is differentiable on R, then 48(a+b) is equal to .
Answer
15
Solution
f is even, checking x=2 is enough (x=-2 is its mirror image)
Continuity at x=2: 4a+2b= 12 ...(1)
Differentiability at x=2: LHD =2a(2)=4a
RHD =- 1x2 at x=2 =- 14
4a=- 14 a=- 116
(1) 2b= 12+ 14= 34 b= 38
48(a+b)=48 516=15
Answer: 15