Stop losing points to sign errors

Most "careless" algebra mistakes are one minus sign in one of four places. Know the four and you'll catch them.

1. Subtracting a negative

5 − (−3) = 5 + 3 = 8. Two minuses next to each other make a plus.

2. A negative outside brackets

−(x − 4) = −x + 4. The minus reaches every term inside, not just the first.

3. Moving a term across the equals sign

x − 7 = 3 becomes x = 3 + 7. Whatever you do to one side, do to the other, and the sign of the term you moved flips.

4. Squaring a negative

(−3)² = 9, but −3² = −9. The brackets decide whether the minus gets squared.

The check that catches all four

Put your answer back into the original problem, not your last line. If the two sides don't match, go back line by line until they do; the line where they stop matching is the slip.