Question

Tangent to parabola $y^2=4x+5$ which is parallel to $y=2x+7$

• A. $y-2x-3=0$
• B. $y=x+3$
• C. $y-2x+1=0$
• D. $y=x+1$

Answer 1

The correct option is A $y-2x-3=0$

Given, $y^2=4x+5$

$\therefore 2y\frac{dy}{dx}=4$

$\therefore \frac{dy}{dx}=\frac{2}{y}=2,$ (given)

$\therefore y=1\Rightarrow x=-1$

$\therefore$ required tangent is given by, $y-1=2(x+1)$ or $y=2x+3$