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Question: Answered & Verified by Expert
Let f(x)=x3 and g(x)=3x, then the quadratic equation whose roots are solutions of the equation (fg)(x)=(gf)(x) (for x0) is
MathematicsFunctionsAP EAMCETAP EAMCET 2021 (20 Aug Shift 1)
Options:
  • A x2-6x+3=0
  • B x2-6x+9=0
  • C x2-x+3=0
  • D x2-3=0
Solution:
2550 Upvotes Verified Answer
The correct answer is: x2-3=0

Let f(x)=x3 and g(x)=3x

(fg)(x)=(gf)(x)             (for x0

(f g )(x) = f( g (x) ) = f( 3x) = 33x

(g  f)(x) = g( f (x) ) = g( x3) = 3x3

Equating the powers with same base

x3 - 3x = 0

x(x2 - 3) = 0

x2 - 3 = 0x  0 

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