Answer:
The sum is;
[tex]-8x^2-x+5[/tex]Explanation:
We want to know the sum of;
[tex]-3x^2-7x+9\text{ and }-5x^2_{}+6x-4[/tex]Let Add and collect the like terms;
[tex]\begin{gathered} -3x^2-7x+9+(-5x^2_{}+6x-4) \\ =-3x^2-7x+9-5x^2_{}+6x-4 \\ =-3x^2-5x^2_{}-7x+6x+9-4 \\ =-8x^2-x+5 \end{gathered}[/tex]Therefore, the sum is;
[tex]-8x^2-x+5[/tex]