Solution
= Solution
At equality, let $\rho_{\rm cc}=\rho_{\rm dust}=\rho_*$. The <cosmological constant> has $P_{\rm cc}=-\rho_*$, while nonrelativistic matter has $P_{\rm dust}=0$. Therefore
$$
\rho+3P=2\rho_*-3\rho_*=-\rho_*<0.
$$
The <scale factor> consequently has $\ddot a>0$: the expansion is accelerated at $a=a_{\rm eq}$.