Differentiate:

$P(x)=-a\sqrt[3]{x}+bx$

$P^{\text{'}}(x)=-a{x}^{-\frac{2}{3}}+b$

$P^{\text{'}}(x)=-ax+b$

$P^{\text{'}}(x)=3a{x}^{\frac{2}{3}}-b$

$P^{\text{'}}(x)=-\frac{a}{3\sqrt[3]{x^2}}+b$