ight) = rac13 imes rac14 = rac112 $. Thus, the probability of at least one positive is $ 1 - rac112 = rac1112 $. Final answer: $oxed\dfrac1112$.Question: Define $M(u) = u - racu^22$ for all real numbers $u$. If $a_1 = 1$ and $a_n+1 = M(a_n)$ for $n \geq 1$, find $a_3$. - Crosslake