SAT Question f44a29a8: Nonlinear Functions answer and explanation with Desmos solution

Choice A is correct. It's given that an object's kinetic energy, in joules, is equal to the product of one-half the object's mass, in kilograms, and the square of the object's speed, in meters per second. This relationship can be represented by the equation $K=\frac{1}{2}m{v}^2$, where $K$ is the kinetic energy, $m$ is the mass, and $v$ is the speed. Substituting a mass of $4$ kilograms for $m$ and a kinetic energy of $18$ joules for $K$ results in the equation $18=\frac{1}{2}\times 4\times v^2$, or $18=2v^2$. Dividing both sides of this equation by $2$ yields $9=v^2$. Taking the square root of both sides yields $v=-3$ and $v=3$. Since speed can't be expressed as a negative number, the speed of the object is $3$ meters per second.