Introductory Algebra for College Students (7th Edition)

10x$^2$-7
Distribute the negative sign to the parentheses and then subtract vertically. $\qquad7x^2-3$ $\underline{-(-3x^2+4)}$ $\qquad\quad\downarrow$ $\quad7x^2-3$ $\underline{+\,3x^2-4}$ $\quad10x^2-7$