Original equation is [tex]P=kx^{2}[/tex]
So, [tex]kx^{2} =P[/tex] and
[tex]k=\frac{P}{x^{2} }[/tex]
If we compare this equation with the given options, we can easily find that this matches with the last one [tex]k=\frac{p}{2x^{2} }[/tex] with P = p/2.
Hence, correct option is [tex]k=\frac{p}{2x^{2} }[/tex].
