Question

Equation of the tangent at (4 , 4) on $x^2$ = 4y is

• A. $2x+y+4=0$
• B. $2x-y-4=0$
• C. $2x+y-12=0$
• D. $2x+y+12=0$

Answer 1

The correct option is B $2x-y-4=0$

Given,

$x^2=4y$

$\Rightarrow 2x=4\frac{dy}{dx}$

$\therefore \frac{dy}{dx}=\frac{x}{2}$

${\frac{dy}{dx}}_{(4,4)}=\frac{4}{2}=2$

equation of tangent,

$(y-y_1)=m(x-x_1)$

$y-4=2(x-4)$

$y-4=2x-8$

$2x-y-4=0$