Question

Simplify: $-m+n-\left[2m-\left\{m-3\left(m+n\right)-\left(2m-n\right)\right\}\right]$

Answer 1

Given that: $-m+n-\left[2m-\left\{m-3\left(m+b\right)-\left(2m-n\right)\right\}\right]$

Simplifying an expression: If there is a ‘+’ sign before a bracket, then the signs of the terms inside the bracket do not change. If there is a ‘-’ sign before a bracket, then the signs of all the terms inside the bracket change.

$$\begin{gathered} -m+n-\left[2m-\left\{m-3\left(m+n\right)-\left(2m-n\right)\right\}\right] \\ =-m+n-\left[2m-m+3m+3n+2m-n\right] \\ =-m-2m+m-3m-2m+n+n-3n \\ =-7m+2n-3n \\ =-7m-n \end{gathered}$$

Therefore, we get $-7m-n$.