Biology Laudelout $^{27}$ used the equation $Q(t)=a t+b e^{-k t}$ to mathematically model the amount $Q$ of carbon dioxide at time $t$ from microbial biomass in soil. Take $a=b=1$ and $k=5,$ graph on your grapher, and locate the approximate value of $x$ for which the amount of carbon dioxide changes from decreasing to increasing. Verify using calculus.