MCQ
A function $f,$ defined for all positive real numbers, satisfies the equation $f(x^2) = x^3$ for every $x > 0$ . Then the value of $f ‘ (4) =$
  • A
    $12$
  • $3$
  • C
    $3/2$
  • D
    cannot be determined

Answer

Correct option: B.
$3$
b
$2x f ‘ (x^2) = 3 x^2 ; 4 f ‘ (x) = 12 ==> f ‘ (4) = 3$ 

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