Why does my child solve −2x > 6 as x > −3?
Your child doesn't reverse the inequality sign when multiplying or dividing by a negative number, such as -2x > 6 giving x > -3.
Why children do it
Inequalities are solved like equations, with one exception: multiplying or dividing both sides by a negative number reverses the sign. Children who treat them exactly like equations miss it. Trying a number shows it: x = 0 fits x > −3, but makes −2x = 0, which isn't more than 6. The answer is x < −3.
How to help at home
Ask them to try a number in their answer and in the question: does it work in both?
The right way
Solve: −2x > 6
- x < −3Divide both sides by -2, and reverse the sign.
Find out where your child is
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