The error is in the distribution property application, in the way the signs are multiplied.
We will look at it in detail:
[tex]\begin{gathered} -2(4-6h)+9 \\ \lbrack(-2)(4)+(-2)(-6h)\rbrack+9 \\ (-8+12h)+9 \\ 12h+1 \end{gathered}[/tex]When (-2) is multiplied by (-12h) it should end with a positive sign, as (-a)*(-b)=a*b
