99 Percentile Qs Bank for JEE MainMathematicsFunctions
If is such a minimum value for which the inverse of f(x)=x^2+3 x-3 exists in [ , ) and g is the inverse of the f , then at x= + 5 2 , d g d x
Options
- A1 2
- B1 3
- C1 4
- D1 5
Correct answer
D. 1 5
Step-by-step solution
We have, f(x)=x^2+3 x-3 y=x^2+3 x-3 y=x^2+3 x-3+ 9 4 - 9 4 y= (x+ 3 2 )^2- 21 4 y+ 21 4 = (x+ 3 2 )^2 x+ 3 2 = y+ 21 4 x= y+ 21 4 - 3 2 f⁻¹(y)= y+ 21 4 - 3 2 f⁻¹(x)= x+ 21 4 - 3 2 =g(x) (given) Minimum value of f⁻¹(x) is -3 2 =- 3 2 x= + 5 2 =- 3 2 + 5 2 = 2 2 =1 Now, g(x)= x+ 21 4 - 3 2 g^ (x)= 1 2 x+ 21 4 at x=1, g^ (x)= 1 2 1+ 21 4 = 1 5