Math 1 · Lesson 3 · Step One · part 3 of 9
The one move, in two places
Subtraction and division translate the exact same way.
The one move, in two places
Subtraction and division translate the exact same way. Change the operation to its partner, and swap in the inverse from Lesson 1.
Subtraction → addition
a − b = a + (−b)
Change − to +, and use the opposite (the additive inverse). "Subtract 5" becomes "add negative 5."
Division → multiplication
a ÷ b = a × 1b
Change ÷ to ×, and use the reciprocal (the multiplicative inverse). "Divide by 2" becomes "multiply by one-half."
| Nickname | Real form | The partner you swap in |
|---|---|---|
| a − b | a + (−b) | the opposite of b |
| a ÷ b | a × 1b | the reciprocal of b |
Same idea both times. That is why Lesson 1 taught opposites and reciprocals together: they are the two undo partners, and this is where you use them.