BITSAT2010MathematicsApplication of DerivativesActual
Let ( f ( x )= ) ( array l a x^2+1, x > 1 x+a, x 1 array . ). Then (f(x) ) is derivable at (x=1 ), if
Options
- A(a=2 )
- B(a=1 )
- C(a=0 )
- D(a=1 / 2 )
Correct answer
D. (a=1 / 2 )
Step-by-step solution
( aligned & Lf ^ (1)= _ h 0 f(1-h)-f(1) -h & = _ h 0 (1-h+a)-(1+a) -h = _ h 0 -h -h =1 & Rf ^ (1)= _ h 0 f(1+h)-f(1) h & = _ h 0 [a(1+h)^2+1 ]-(1+a) h & = _ h 0 (a h+2 a)=2 a aligned ) Since f' (1) exists, ( L f^ (1)=R f^ (1) a=1 / 2 )