$$ \begin{aligned}-2a+5acube+1-10& \xlongequal{ }-2a+5abceu+1-10 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}5abceu-2a-9\end{aligned} $$ | |
① | Combine like terms: $$ -2a+5abceu+ \color{blue}{1} \color{blue}{-10} = 5abceu-2a \color{blue}{-9} $$ |