Why does my child think 7x − 2 − 3x + 4 = 10x + 2?
Your child loses the minus sign in front of a term when collecting like terms, such as 7x - 2 - 3x + 4 = 10x + 2.
Why children do it
When terms are moved around to collect them, the sign in front of each term has to go with it. Children who move the 3x without its minus sign add it instead of taking it away. 7x − 3x is 4x, and −2 + 4 is 2, so the answer is 4x + 2.
How to help at home
Ask them to circle each term with the sign in front of it before collecting.
The right way
Simplify: 7x − 8 − 3x + 7
- 7x − 3x − 8 + 7Move each term with the sign in front of it.
- 4x − 17x − 3x is 4x, and -8 + 7 is -1.
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