Answer
3x$^2$-7x+9
Work Step by Step
Distribute the negative sign to the parentheses and then combine like terms vertically.
$\quad7x^2-9x+2$
$\underline{-(4x^2-2x-7)}$
$\qquad$$\quad$$\downarrow$
$\quad7x^2-9x+2$
$\underline{-4x^2+2x+7}$
$\quad3x^2-7x+9$
