The speed v of a particle moving along a straight line is given by $a+b v^2=x^2$ where x is its distance from the origin. The acceleration of the particle is

$\frac{x}{b}$ $\frac{x}{a b}$ $a b x$ $a x$

$\frac{x}{b}$

We have, $a+b v^2 =x^2$ $\Rightarrow 2 b v \frac{d v}{d x} =2 x \Rightarrow v \frac{d v}{d x}=\frac{x}{b}$ ⇒ Acceleration = $\frac{x}{b}$