AP EAMCET2015MathematicsFunctions
If f: R R, g: R R are defined by f(x)=5 x-3, g(x)=x^2+3 , then g f⁻¹(3) is equal to
Options
- A25 3
- B111 25
- C9 25
- D25 111
Correct answer
B. 111 25
Step-by-step solution
Given, f(x)=5 x-3 and g(x)=x^2+3 Let, y=f(x), y=5 x-3 aligned & y+3=5 x x= y+3 5 & f⁻¹(y)= y+3 5 f⁻¹(x)= x+3 5 aligned Now, g(x)=x^2+3 ; So, g f⁻¹(3)=g [f⁻¹(3) ] =g ( 3+3 5 )=g ( 6 5 )= (6)^2 (5)^2 +3= 36 25 +3= 111 25