If f 1 = 1 , f ' 1 = 3 , then the derivative of f f f x + f x 2 at x = 1 is:

If f1=1,f'1=3, then the derivative of fffx+fx2 at x=1 is:
  1. 9
  2. 12
  3. 15
  4. 33

Solution

y=fffx+fx2

⇒dydx=f'ffx×f'fx×f'x+2fx×f'x

⇒dydxx=1=f'ff1×f'f1×f'1+2f1×f'1

=f'f1×f'1×3+2×1×3

=f'1×3×3+6

=3×3×3+6

=27+6

=33

Asked in: JEE Main 2019 (08 Apr Shift 2)

Practice more Differentiation questions on Aicharya