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For the specified flat matter-vacuum model,Its small-redshift behaviour is $F(z)=0.55z+O(z^2)$, since $q_0={\Omega }_{m,0}/2-{\Omega }_{\Lambda ,0}=-0.55$. At high redshift, matter dominates and $F\sim -\sqrt{0.3}{s}^{3/2}$, so the initially positive redshift drift must turn negative. To locate the crossing, square $s=\sqrt{0.3s^3+0.7}$; both sides are positive, so squaring introduces no positive-$s$ spurious root. Factorization givesBesides $z=0$, the physical nonzero redshift-drift root in flat matter-Lambda cosmology isThe redshift drift is positive for $0<z<z_{\ast }$ and negative for $z>z_{\ast }$. Its maximum satisfies $1=0.45s^2/\sqrt{0.3s^3+0.7}$ and lies near $z=0.949$, where $F\simeq 0.240$. This zero is distinct from the acceleration transition at $z_{\mathrm{acc}}=(2{\Omega }_{\Lambda ,0}/{\Omega }_{m,0}{)}^{1/3}-1\simeq 0.671$: redshift drift compares expansion at two epochs, while acceleration is local to one epoch.