Chapter 8 · Habits · page 36 of 68
The sign belongs to the term
levelAll
standardEverywhere
practiceMixed practice
In 3 − 3 × 7, the minus is not an operation floating between things. It belongs to the 3 × 7 term. Read it as 3 + (−21). This one habit prevents most sign errors in arithmetic, in combining like terms, and in equations.
How to use it
- When you split an expression into terms, take each sign with the term after it.
- Rewrite subtraction as adding a negative when things get complicated.
- Then you can add terms in any order.
Example
Where it goes wrong
- Computing 21 − 3 instead of 3 − 21.
- Losing a minus when reordering terms.