Answer
Decreasing
Work Step by Step
Given $$\left\{ n- n^2\right\}_{1}^{\infty}$$
Since $a_n=n- n^2,\ \ a_{n+1}= n+1- (n+1)^2$, then
\begin{align*}
a_{n+1}-a_n&= n+1- (n+1)^2-n+n^2\\
&= n+1-n^2-2n-1-n+n^2\\
&= -2n\leq0
\end{align*}
So, the sequence is strictly decreasing