[tex]\bf (4x^2-x+1)~~+~~(-6x^2+x-4)\implies 4x^2-x+1~~~~-6x^2+x-4 \\\\\\ 4x^2-6x^2-x+x+1-4\implies \stackrel{\textit{their sum}}{-2x^2-3}\implies \stackrel{\textit{twice that much}}{2(-2x^2-3)}\implies -4x^2-6[/tex]
