Answer:
[tex]2x^2+9x-6[/tex]
Step-by-step explanation:
Just subtract the two because x + y = z and z-x = y
[tex]3x^2+7x-(x^2-2x+6) = 3x^2+7x-x^2+2x-6\\\\=2x^2+9x-6[/tex]
You can test this by adding this expression back to the original.
[tex]x^2-2x+6+(2x^2+9x-6) = 3x^2+7x[/tex]
