$p=$ $q=$ $f\left(b\right)=$ ${f}^{\prime }\left(b\right)=$ $b=$

solve

$\begin{array}{ll}\hfill & {f}^{\prime \prime }{}^{}=0\text{ }\wedge \text{ }f\left(0\right)=0\text{ }\wedge \text{ }{f}^{\prime }\left(0\right)=0\hfill \\ ⇔\text{ }\hfill & \phantom{\rule{0}{15pt}}f=0\mathrm{}{}^{\mathrm{}}\mathrm{}\mathrm{}{}^{\mathrm{}}\hfill \end{array}$