b) |–28| – |98| = …………………………………………..

c) (–200) – |–25|.|3| = (–200) – 25.3 = –200 – 75 = –275.

a) Do |x| = 4 nên x = 4 hoặc x = –4.

b) Do |x| = $\sqrt{7}$ nên x = $\sqrt{7}$ hoặc x = – $\sqrt{7}$.

c) Do |x + 5| = 0 nên x + 5 = 0 hay x = –5.

d) Do |x – $\sqrt{2}$ | = 0 nên x – $\sqrt{2}$ = 0 hay x = $\sqrt{2}$ .