JEE Main 2014 · 12 Apr · Shift 1 · Mathematics Q71

MathematicsSingle correct+4 / -1Question 71 of 90

If $f(x)=x^2-x+5$ , $x>\dfrac12$ , and $g(x)$ is its inverse function, then $g'(7)$ equals :

-\dfrac13

\dfrac1{13}

\dfrac13

-\dfrac1{13}

Answer and worked solution

Official answer: C

$f(x)=7$ with $x>\frac12$ gives $x=2$ . $f'(2)=2(2)-1=3$ , so $g'(7)=\dfrac1{f'(2)}=\dfrac13$ .

JEE Main 2014 · 12 Apr · Shift 1, Mathematics question 71