Why does my child think −2(x − 3) = −2x − 6?
Your child gets a sign wrong when multiplying out a bracket by a negative number, such as -2(x - 3) = -2x - 6.
Why children do it
With a negative number outside the brackets, every term inside changes sign, and the second one is the easy one to miss. −2 times −3 is positive 6, because two negatives make a positive. So −2(x − 3) is −2x + 6.
How to help at home
Ask them to multiply the negative number by each term in turn, saying the sign each time.
The right way
Expand: −4(x − 2)
- −4 × x + (−4) × (−2)Multiply each term by -4, signs and all.
- −4x + 8A negative times a negative is positive.
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